Morgan McSweeney quits as Keir Starmer’s chief of staff over the Peter Mandelson–Epstein scandal, leaving the British prime minister fighting for his political survival.
British Prime Minister Keir Starmer lost his most senior aide on Sunday as the political crisis over Peter Mandelson's ties to convicted sex offender Jeffrey Epstein threatened to end his leadership 18 months after Labour's landslide election victory.
Morgan McSweeney resigned as Downing Street chief of staff, saying he took "full responsibility" for advising Starmer to appoint Mandelson as UK ambassador to the United States in December 2024.
"The decision to appoint Peter Mandelson was wrong. He has damaged our party, our country and trust in politics itself," McSweeney said in a statement.
The 48-year-old strategist was the architect of Labour's July 2024 election triumph and Starmer's closest political adviser since he became party leader in 2020.
His departure leaves Starmer further weakened as opposition leaders demand his resignation and Labour MPs question whether he can survive in office.
New Epstein files deepen crisis
After the US Department of Justice latest release of 3 million pages of documents relating to Epstein, fresh details emerged about Mandelson's relationship with the disgraced financier and convicted child sex offender who died in prison in an apparent suicide in 2019.
The files include emails suggesting Mandelson shared market-sensitive government information with Epstein in 2009 while serving as business secretary during the global financial crisis under then-Prime Minister Gordon Brown.
Documents also show alleged payments totalling $75,000 (€63,200) from Epstein to accounts linked to Mandelson or his partner in 2003 and 2004.
Metropolitan Police officers searched two properties linked to Mandelson on Friday as part of an investigation into potential misconduct in public office, which carries a maximum sentence of life imprisonment.
Mandelson has not been arrested or charged. His lawyers said he "regrets, and will regret until his dying day, that he believed Epstein's lies about his criminality" and did not discover the truth until after Epstein's death.
Starmer appointed Mandelson to Britain's most important diplomatic post in December 2024 despite knowing he had maintained contact with Epstein after the financier's 2008 conviction for soliciting prostitution from a minor.
The British PM fired Mandelson in September 2025 when earlier revelations about the relationship emerged.
Starmer apologised to Epstein's victims on Thursday, saying: "I am sorry. Sorry for what was done to you, sorry that so many people with power failed you, sorry for having believed Mandelson's lies and appointing him."
He has promised to release documentation about Mandelson's vetting, which the government says will show the former minister misled officials about his ties to Epstein.
Mandelson resigned from the Labour Party on 1 February and quit the House of Lords on Wednesday.
Opposition smells blood
Conservative Party leader Kemi Badenoch said Starmer's position is "untenable" and called on him to take responsibility for the appointment.
"Keir Starmer has to take responsibility for his own terrible decisions. But he never does," she said.
Reform UK leader Nigel Farage predicted Starmer would not survive beyond May's local elections.
Political analysis firm Eurasia Group now puts the probability of Starmer's removal from office this year at 80%.
Some Labour MPs have questioned whether Starmer can remain in post, though no clear leadership challenger has yet emerged.
Starmer has failed to deliver promised economic growth or repair public services during his 18 months in office.
Labour consistently trails the hard-right Reform UK party in opinion polls, and the government has been hit by policy U-turns over welfare cuts and other unpopular measures.
Morgan McSweeney's loss is the latest in a series of setbacks for a prime minister who won one of the largest parliamentary majorities in modern British history.
Under Britain's parliamentary system, prime ministers can be replaced without a general election. If Starmer were challenged or resigned, Labour MPs would elect a new party leader who would become prime minister.
The Conservatives cycled through three prime ministers between the 2019 and 2024 elections, with Liz Truss lasting just 49 days in office.
Starmer campaigned on ending the political chaos of those Conservative years — a promise that now appears increasingly difficult to keep.