Despite his government being elected with a huge majority of 172 in July 2024, Sir Keir's support base was described as "wide but shallow".
Big promises on key issues, including easing the cost of living, restoring the NHS and dealing with an acute housing crisis, had been the cornerstone of his pledges to win over the electorate.
Now, just under two years later, he has resigned. The exact timetable for his departure is unclear, but we know that he will become the shortest-serving Labour prime minister in history.
His replacement will be the seventh prime minister in 10 years, following years of increasing instability and high turnover at the top of government.
Cost of living
Sir Keir has emphasised that cutting the cost of living was his government's "number one priority".
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Consumer price inflation surged from 2.2% to 3.8% in Starmer's first year in power. But, despite the impact of the conflict in the Middle East on trade, it has since fallen back to 2.8%.
That's still higher than the target rate, but lower than many experts predicted it would get to when it became clear that the Iran war would not be over quickly.
The war added to a series of external shocks that also included Donald Trump's sweeping tariffs on US imports.
Sir Keir pledged to make the UK the fastest-growing economy in the G7 by the end of this parliament. While UK economic growth has been slow - at 1% in 2025 - the country is not alone in facing economic challenges, and is currently outperforming several G7 peers as the second-fastest growing economy in the group over the past 12 months.
Britain's growth figures for March showed an unexpected rise, but the most recent figures - for April - showed a contraction of 0.1%.
Tax thresholds
While the Government has repeatedly promised not to increase taxes for working people, "stealth" tax increases through frozen tax thresholds mean many are paying more.
Tax thresholds have been frozen since 2021 and are set to remain frozen until 2028.
That means that as inflation leads to wage increases, we end up paying more tax on a higher proportion of our earnings - a process known as fiscal drag.
Missing housebuilding targets
Slow economic growth and persistent cost of living issues may have contributed to the prime minister's unpopularity, but they have also made it harder to deliver in other areas, like housing.
Sir Keir said he wanted to "build baby, build", summing up his government's ambitious promise of creating 1.5 million additional homes before the next general election.
Achieving it would represent a higher level of housebuilding than at any point since the post-war period.
With the halfway point of this parliament fast approaching, housing delivery has fallen to its lowest level in nine years.
Housebuilders have raised concerns that building is "flatlining" and no longer viable - particularly in London, where only 5,000 new homes were started in the latest year, against a target of 81,000.
Based on analysis of new Energy Performance Certificates (EPCs), which are a strong indicator of additional housing supply, Sky News estimates around 353,000 additional homes have been delivered under Labour, short of the 525,000 that would have been required so far to be on track to meet targets.
While the Government has always maintained that the pace will increase towards the end of the parliament, the current shortfall of nearly 200,000 is close to a whole year's housebuilding at the current pace.
NHS promises
Fixing the "broken" NHS has been another key pledge under Sir Keir's leadership.
The Government is quick to point out that NHS England's waiting list is down by more than 500,000 appointments, from 7.62 million in July 2024 to 7.11 million appointments in the latest figures for March 2026.
It remains substantially higher than the 4.57 million appointments pre-pandemic in February 2020, however. More than one in 10 people in England are currently waiting for some sort of NHS treatment.
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The Government has a target that, by the time of the next election, no more than 8% of patients should wait more than 18 weeks to start their treatment.
The figure was up at 41% when Labour took over in July 2024, and they had an interim target to have reached 35% by March 2026.
They achieved that target in March, but fell back again in April so the latest figures are back underneath that target.
Much of the improvement is also thanks to "unreported removals" - people removed from the waiting list for reasons other than receiving treatment. March 2026 had the highest number of "unreported removals" since the pandemic.
Meanwhile, "trolley waits" - where patients wait for long periods in corridors for hospital beds - reached a new record high, with 554,000 waits of more than 12 hours in 2025. That was more than the total recorded between 2011 and 2022.
Migration battle
According to Donald Trump's analysis, delivered via his Truth Social platform on Sunday, Starmer has been forced to resign after "failing on two very important subjects - IMMIGRATION AND ENERGY".
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Fact-checked: Is Trump right about Britain having the highest energy prices?
On immigration, Sir Keir can certainly point to some successes, although his record overall has been patchy.
He inherited certain troubles from the previous Conservative government while also benefiting from the effects of the outgoing government's policies to reduce visa routes.
Net migration was already in decline by the end of the Conservative government's tenure, but has fallen to just 204,000 year-on-year under Labour - down 68% from June 2024 levels - and is now inline with pre-Brexit and pre-Covid levels, the lowest in more than five years.
Last year also saw the highest number of returns (38,000 in total) in nearly a decade, meaning more immigrants leaving the UK either by voluntary or enforced return.
But one of Labour's pledges was to "smash the gangs", referring to people-smuggling gangs who facilitate deadly English Channel crossings.
Small boat crossings skyrocketed under Sir Keir with more than 75,000 recorded under his leadership - more than any other prime minister. Both 2024 and 2025 were two of the highest years on record for illegal Channel crossings, behind the peak in 2022.
Latest figures show crossings going down from their recent peak, however. The number of boats that have arrived in the last year is lower than at any point since 2020.
But as the number of people per boat has been rising, the number of people that have crossed in the past 12 months remains above the level inherited by Labour.
Although Sir Keir successfully passed the Border Security, Asylum and Immigration Act, alongside boosting enforcement staffing and powers by creating a Border Security Command, these have yet to meaningfully manifest in widescale prevention of small boat crossings.
U-turns and scandals
Since entering government, Sir Keir Starmer's Labour has been marred with political unrest and accused of rowing back on several of its manifesto commitments.
Despite his massive majority, his own MPs forced him to change course on several important policy areas, like winter fuel payments for pensioners, personal independence payments for disabled people, and the benefit cap for parents with more than two children.
Protests from the farming lobby also forced changes to his policy on inheritance tax for agricultural properties. And a legal challenge from Reform UK led to the government reversing a decision to cancel a significant number of council elections.
Explore our timeline for more detail.
The prime minister has also faced resignations and controversy from those closest to him, from two chiefs of staff to his deputy Angela Rayner.
Arguably the most significant of these scandals has been the appointment of Lord Peter Mandelson as UK ambassador to the US, with subsequent revelations from the Epstein files revealing that the Labour figure had a much closer relationship with the convicted paedophile than previously believed.
Sir Keir Starmer repeatedly faced criticism over the vetting process amid Lord Mandelson's resignation and later arrest.
By-election defeat
Rumours over a leadership challenge from Andy Burnham began last September around the time of the Labour Party conference, but the Manchester mayor was barred from running for a constituency seat in the Gorton and Denton by-election this year. The party lost the seat to the Green Party.
When Mr Burnham was allowed to run, in Makerfield last week, the contrast was clear. Labour's vote share increased by 9.6 percentage points compared with the 2024 general election, and on an increased turnout too.
Mr Burnham's victory was the first time since 1997 that Labour had secured a vote share increase at a by-election while in government.
Political performance
Recent local elections across England, where Labour lost nearly 1,500 council seats and control of 40 councils, have ultimately forced Sir Keir Starmer's decision to no longer lead Labour into the next general election.
Overall, Labour has defended 2,853 seats in local elections since 2024 and lost 1,697 of them - a loss rate of 59%. As a result, their share of total councillor numbers in England has dropped to just over 25% so far, although not all seats have had new elections in that time.
The last time they had a smaller share of councillors was just before they lost the 2010 election.
Labour also saw disastrous results in elections in Wales and Scotland.
They lost control of the Welsh Senedd for the first time after their vote share fell to just 11.1%.
They also recorded their worst result in a Scottish parliament election, winning just 17 of 129 seats in Holyrood, down from 22 in 2021.
Welsh Labour leader Eluned Morgan resigned after losing her seat, while Scottish Labour leader Anas Sarwar placed the blame with Sir Keir, calling it "a big national wave and a general vibe that we couldn't change".
That led to weeks of Sir Keir facing calls to resign from 100 of his own MPs, including his foreign secretary Yvette Cooper and former health secretary Wes Streeting. John Healey also resigned as defence secretary over a military funding dispute.
General election threat
Underpinning a lack of confidence in Starmer is the anxiety around Labour's prospects of remaining in power for a second term, which is looking increasingly difficult on current voting trends.
Should voting patterns from recent local elections be replicated at the next general election, Sky's election expert Professor Michael Thrasher has projected a redistribution of each party's seats in the House of Commons.
The result would be a hung parliament with no single party able to pass the threshold of 326 seats required for an overall majority, but with Reform as the largest party, and Labour's seats reduced to just 110 - which would be their lowest since 1931.
Unpopular with the public
Sir Keir delivered on some of his key manifesto promises - such as introducing the Renters' Rights Act which abolished no-fault evictions, among other improved rights for renters.
The Employment Rights Act has also so far delivered enhanced rights for employees, with day-one entitlement to sick pay and other protections from April 2026.
The prime minister's stance on Iran in resisting US President Donald Trump's pressure to become fully involved may also have contributed to a small recent bump in his net approval ratings.
Despite this, Sir Keir remains unpopular overall, with 69% viewing him unfavourably in mid May according to polling by YouGov - down from a peak of 75% in January.
Ultimately, it is the prime minister's popularity with the public - and future electability - that has been at the front of Labour MPs' minds.
Compared with other recent resigning prime ministers after a similar length of time in office, Sir Keir is less popular than all but Liz Truss, at -38% approval overall.
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The 63-year-old committed the crimes between 1985 and 2008, when the two women were children.
He denied all the charges, calling them "simply not true" and "just unbelievable", but the jury on Monday convicted him of rape, 13 indecent assaults and four counts of gross indecency.
The former MP, once Northern Ireland's best-known politician, stood with his hands folded and showed no reaction.
Both victims gave evidence during the trial in Newry, as did Donaldson over two days earlier this month.
His wife, Lady Eleanor Donaldson, was found to have aided and abetted his crimes.
She faced a trial of the facts on mental health grounds, which tested the evidence but could not result in a criminal conviction.
The former DUP (Democratic Unionist Party) leader was found guilty of nine indecent assaults and one rape, between 1985 and 1991, against the older of the two women (Complainant B).
The other victim (referred to in court as Complainant A) was abused between 1999 and 2008 and said she was first abused when she was primary school age.
She told the jury Donaldson used a light, possibly a torch, to look at her "private parts" and that she had told his wife about the incident.
The woman told the court: "I knew by the look on her face she knew I was telling the truth… once she identified I was telling the truth, she did nothing about it."
She said the couple had "laughed off" an incident where Donaldson put his tongue in her mouth, and claimed he touched her breasts "skin on skin" when she was a child.
The jury heard Donaldson sent her letter in 2020 expressing "regret" for "all the hurt, pain and distress I have caused". The former politician claimed it was about other behaviour and not related to sexual abuse.
The older woman (Complainant B) told the court she remembered two incidents "vividly".
She said Donaldson had put his hand down her underwear, pulled her legs apart with his feet and raped her. Like the other victim, she said it happened when she was of primary school age.
The second incident she described was Donaldson lifting her top and touching her breasts when she was at secondary school.
She told the court Eleanor Donaldson had witnessed part of the incident but "walked away".
When challenged by the defence, she replied: "Everything I am saying is the truth… no matter how many questions people ask me it will never change that."
'Destroy their political reputation'
The woman said some of the abuse by Donaldson was while she stayed at the Christian Family Centre in Armoy in the 1990s, when she was having problems with drugs.
Claire Selfridge, daughter of the centre's founders, testified that Complainant B had told her she'd been abused in her bedroom.
A police interview with Pastor Stephen Matthews was also played in court.
He said she'd told him about the abuse but urged him not to contact the authorities as "it would destroy their political reputation" and she didn't want that.
Audio of the Donaldsons' police interviews was also played in court.
In one section, the former DUP leader was asked about the rape and replied: "I'm sorry, but I can't get my head around this notion."
Asked about the claim he used a light to look at Complainant A's body, he told police he "wasn't doing anything untoward".
Mrs Donaldson was heard telling officers in interview that the claims were a "massive, massive shock".
Regarding the rape allegation, she told them: "I would say that didn't happen. Absolutely not, oh my goodness."
Jeffrey Donaldson's lawyer, Kieran Vaughan KC, said there were "significant and fundamental issues" with the women's credibility. However, prosecutor Rosemary Walsh told jurors there was "no reason" for the women to lie.
"What the evidence shows when it is pieced together is that they are telling the truth about what happened to them," she said in her closing speech.
Jeffrey Donaldson has been remanded into custody and will be sentenced later this year. The judge told him to expect a "lengthy" sentence.
The boy is at Addenbrooke's Hospital, in Cambridge, after Thursday's incident at Johnsons of Old Hurst, near Huntingdon.
Cambridgeshire Police told Sky News: "The toddler remains in Addenbrooke's and is in a stable condition."
It is understood the boy was attacked by at least one crocodile after he was allegedly thrown into the enclosure.
A 30-year-old man was arrested on suspicion of attempted murder.
Police said the arrested man, from Norfolk, was "assessed as not being fit for interview" and has been released on bail until September.
Police were called to the zoo at 1.24pm by the ambulance service to reports a boy had suffered serious injuries.
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Cambridgeshire Police said the boy "sustained serious injuries while in the enclosure" and "was pulled out by staff from the zoo".
Police said the boy "received medical treatment at the scene before being taken to hospital".
The zoo is home to more than 100 animals, including crocodiles, Bengal tigers, African lions, capybaras, meerkats, and sloth bears, according to its website.
Moscow mayor Sergei Sobyanin said on Telegram that 84 drones had been intercepted in the past 24 hours.
Emergency services were sent to debris fallout areas but the mayor offered no word on casualties or damage.
In total, some 301 drones were downed overnight, according to Russian news agencies, though the figure includes Russian-occupied areas of Ukraine.
Flights were also stopped at Moscow's four main airports but have since resumed, an aviation watchdog said.
Ukraine's military general staff said it had also attacked the Dubna satellite communications centre in the Moscow region.
On Telegram, it shared a picture of thick black smoke and said it was assessing the damage.
The post detailed other strikes; including on a drone operator "training ground" in the Debaltseve area of Luhansk, and on "command and observation points" in the Russian border region of Belgorod and the Pokrovsk area of Donetsk.
Another post claimed a factory producing electronics for Russian missiles had been struck in Voronezh, more than 100 miles from Ukraine.
The attacks come after a Ukrainian drone strike damaged an oil refinery in Moscow last week in one of the biggest such attacks on the capital since the war began.
That in turn followed an attack on St Petersburg as a high-profile economic forum got under way at the start of June.
Such attacks - which President Zelenskyy calls "long-range sanctions" - are seen as an attempt to bring the war home to ordinary Russians and pressure President Putin to negotiate.
Russia also continued its own attacks on Ukraine overnight into Monday.
Prosecutors said a 13-year-old boy had been killed alongside his father and grandmother in a drone strike in the Sumy region. His mother and two siblings were injured.
A woman also died in an attack in the southeastern city of Zaporizhzhia, while a missile attack on an agricultural facility killed one person in the Odesa region.
The regions' governors detailed the attacks on Telegram and said six people had also been injured.
Three foreign ships were also hit overnight, according to Ukraine's deputy prime minister Oleksiy Kuleba.
He said on Telegram that a 58-year-old Egyptian cook had been killed when drones badly damaged a Turkish dry cargo vessel. Eight other crew evacuated on a lifeboat.
Ships operating under the flags of Palau and Belize were also attacked, Mr Kuleba said, adding that there were no injuries and the vessels had continued their journeys.
Russia has repeatedly targeted ships and ports vital to Ukraine's foreign trade and the wartime economy.
Meanwhile, open-air public events have been cancelled on Monday in Sevastopol, in Russian-annexed Crimea.
Governor Mikhail Razvozhayev urged people to save electricity and said street lights would also stay off.
Ukrainian attacks on energy facilities and supply routes have led to a fuel crisis there, with supplies currently restricted to agencies responsible for essential services and security.
The man, who is in his 60s and from the Stockport area - but cannot be named because it would identify the alleged victim - had previously denied 48 charges.
He appeared at Manchester Minshull Street Crown Court on Monday, where he pleaded guilty to 12 of the offences, including two counts of rape, three counts of sexual assault, six counts of assault by penetration and a charge of sharing intimate images.
The offences took place over a three-year period between March 2022 and October last year.
Thirteen other men aged between 28 and 73, who cannot be identified for legal reasons, have also been charged with alleged offences relating to the same woman.
Her husband allegedly drugged her in order to rape and sexually assault her on his own over more than two decades since 2004.
Between 2018 and his arrest last year, he allegedly invited other men to sexually assault and rape his wife while she was unconscious.
All of the other men are charged with conspiracy offences, and 10 of them are alleged to have also committed so-called contact sexual offences with the husband.
A man in his 50s previously pleaded guilty to charges of conspiracy to rape, conspiracy to assault by penetration, conspiracy to administer a substance and assault by penetration.
All of the other men deny the charges against them and face trial at the same court on 1 September.