Why did Sir Keir Starmer resign?

Sir Keir Starmer has announced his decision to step down as prime minister.

Speaking outside Number 10 on Monday morning, the PM said he accepts "with good grace" that Labour MPs do not want him to lead them into the next general election.

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The resignation comes less than two years after Labour's landslide win at the polls in 2024 - so where did it all go wrong?

Here are some of the key moments that have contributed to Sir Keir's exit...

Mandelson vetting scandal

The Peter Mandelson vetting controversy was arguably the most significant scandal Sir Keir faced during his premiership.

The influential Labour figure was announced as UK ambassador to the US in December 2024. But less than a year later, in September 2025, Mandelson was fired after leaked emails revealed he remained in contact with Jeffrey Epstein after his 2008 conviction for soliciting a minor for prostitution.

The release of the Epstein files in February then revealed Lord Mandelson allegedly leaked information to the paedophile financier while serving as a Labour minister in 2009.

In the wake of the revelations, Number 10 faced scrutiny over how Mandelson's appointment had been allowed in the first place - and it soon emerged that he had failed the security vetting process.

Sir Keir survived the scandal, with his chief of staff Morgan McSweeney taking "full responsibility" for advising the PM to appoint Lord Mandelson and resigning from his position.

Gorton and Denton loss

Labour's first defeat of the year came in February, when the Greens' Hannah Spencer won the Gorton and Denton by-election.

Labour had won the seat at the last general election by over 50%, but found itself pushed into third as Ms Spencer secured 40% of the vote, with Reform candidate Matt Goodwin in second place.

The defeat was especially damaging as Sir Keir had blocked Andy Burnham from standing as Labour's candidate in the by-election.

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May local election results

Less than three months after the Gorton and Denton result, most of the UK went to the polls with elections for councils in England, the Scottish Parliament and the Welsh Senedd.

It was a disaster all round for Labour, with the party losing more than 1,200 English council seats and - for the first time ever - control of the Welsh Senedd.

The results led to more than 90 Labour MPs calling for Sir Keir to resign, including his foreign secretary Yvette Cooper and then health secretary Wes Streeting.

Approval ratings

Labour has struggled in the opinion polls - with Sir Keir's satisfaction ratings falling to the lowest level of any PM in the past 50 years.

After winning the general election in July 2024, Labour was initially ahead in the polls for several months.

But by October of that year, their rating had dropped below 30% and continued to slide to the mid-20s by early 2025.

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The second year of Sir Keir's premiership saw Labour's ratings fall further, dropping below 20% in October 2025, while Reform opened up a clear and sustained lead.

The most recent Ipsos survey, from mid-May, suggested 16% of adults were satisfied with Sir Keir's performance and 76% were dissatisfied.

This gave Sir Keir a net approval score of minus 60 - which is lower than any other score recorded by Ipsos for a PM two years after taking office.

Burnham's Makerfield victory

The final nail in the coffin for Sir Keir's stint as PM came last week, when Mr Burnham sailed to victory with his decisive Makerfield by-election win.

The seat's wards had swung hard to Reform in the local elections but swung back just as hard to Labour, with the now former Manchester Mayor securing 54.8% of the votes.

The win was vital for Mr Burnham, who needed to secure a seat in Westminster in order to put himself forward for the Labour leadership.

(c) Sky News 2026: Why did Sir Keir Starmer resign?