Starmer is facing what is widely seen as the gravest crisis of his 18 months in power over his decision to send Mandelson to Washington in 2024, after files revealed the extent of Mandelson’s relationship with the late sex offender Jeffrey Epstein.
The departure of McSweeney, 48, the political strategist who was instrumental in Starmer’s rise to power, throws the future direction of the government into doubt, less than two years after the Labour Party won one of the largest parliamentary majorities in modern British history.
With polls showing Starmer is already hugely unpopular with voters, some in his own party are openly questioning his judgement and his future, and it remains to be seen whether McSweeney’s exit will be enough to silence his critics.
Mandelson’s appointment was ‘wrong’
McSweeney said it was right for him to resign because Starmer had appointed Mandelson on his advice.
“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.
“When asked, I advised the Prime Minister to make that appointment and I take full responsibility for that advice.”
Starmer has spent the last week defending McSweeney, a strategy that could prompt further questions about his own judgement. In a statement on Sunday, Starmer said it had been “an honour” working with McSweeney.
New evidence about Mandelson’s relationship with Epstein came to light in the last ten days, opening an old wound for Starmer and his Labour Party and sparking a police investigation into Mandelson’s alleged misconduct in public office. The files suggested the former ambassador had leaked government documents to Epstein in 2009 and 2010.
Labour members of parliament had called for McSweeney’s resignation, blaming him for the appointment of Mandelson and the damage caused by the publication of the crude exchanges between Epstein and Mandelson.
McSweeney, who was a protege and friend of Mandelson, was accused by some Labour lawmakers and his political opponents of failing to ensure that there were proper background checks when he was appointed.
He had held the role of chief of staff since October 2024, when he was handed the job following the resignation of Sue Gray following a row over pay and donations.