Morgan McSweeney has resigned as the Downing Street chief of staff over his role in the appointment of Peter Mandelson as US ambassador, in what could be a fatal blow to Sir Keir Starmer’s premiership.
Sir Keir’s right-hand man, who was credited with masterminding Labour’s landslide election victory in 2024, has stepped down from the role.
It comes amid mounting on the prime minister himself to quit over the scandal and is already being perceived as a damage limitation exercise to save Sir Keir’s premiership.
Mr McSweeney was seen as instrumental in the appointment of Mandelson to the most important diplomatic post, a decision which has become an embarrassment for the government following the latest revelations about his relationship with convicted paedophile and financier Jeffrey Epstein.

The decision leaves Sir Keir greatly weakened, with the man at the heart of the Starmer project out of government, and there are questions over whether the prime minister can survive in Downing Street without his right-hand man.
It came despite his closest cabinet ally, welfare secretary Pat McFadden, saying that Mr McSweeney, who oversaw Labour’s election victory just 19 months ago with him, should not go.
Mr McFadden dismissed the calls for a change of personnel in Downing street as “beside the point”.
But Lord Blunkett had led the charge for McSweeney to be sacked as the only way Sir Keir can buy himself time to save his badly damaged government.
The former home secretary told BBC Radio 4: “He needs a new chief of staff, he needs an opening up of the routes to him so that people can reach him and he can hear what people are thinking and feeling.”
Meanwhile, a number of leading female Labour figures including Baroness Ayesha Hazarika condemned “the boy’s club” in Downing Street which had led to the appointment of Mandelson as ambassador to the US.
She said: “Everyone knew Mandelson mixed in these circles. The calculation was these are the slightly tawdry circles in which the US President moves… we need a guy who sits in those hot tubs.”
Mr McSweeney, 48, had already been a controversial figure in the Downing Street operation and was facing demands to resign as recently as December, following a hostile briefing from No10 officials about health secretary Wes Streeting.
A close ally of his Paul Ovenden was sacked from Downing Street when emails with lurid remarks about veteran Labour MP Diane Abbott emerged.
But the outgoing chief of staff has had to fall on his sword after pushing for Mandelson to be made ambassador last year, despite concerns from the Donald Trump administration and red flags raised by the security services over the former Labour grandee’s links to China and Epstein.
Revelations that Mandelson leaked confidential and market sensitive government material to Epstein, as well as maintaining contact with the disgraced financier when he had been found guilty of sex crimes, have seen the Labour grandee forced to quit the party and give up his seat in the Lords.
Embarrassing pictures of Mandelson in his underwear with Epstein have also made the affair even more tawdry but there are claims that the security services warned Downing Street of the problems before he was confirmed as ambassador.
However, McSweeney has been accused of wanting to replicate the Tony Blair era of government and relied on big beasts from that period, including Mandelson, who had been his mentor.
To make matters worse when Sir Keir sacked Mandelson as ambassador in September last year it is understood that McSweeney pleaded to keep him in post.
While some believe McSweeney is being made a scapegoat to protect a prime minister whose own position is in doubt, others believed that McSweeney’s position had become untenable.
He had already caused controversy by ousting the previous chief of staff Sue Grey and replacing her just a few months into the government.
As the man who ran the election campaign in 2024, McSweeney, whose wife Imogen Walker is an MP and party whip, was also blamed for the overpromising in the manifesto which is in part responsible for the various U-turns in recent months.
Along with the prime minister he was also blamed for an apparent lack of direction and narrative in a Labour government which has plummeted to below 20 per cent in the polls and never enjoyed a honeymoon period despite winning a huge majority.
The resignation though has not protected Sir Keir from demands he also quit.
Asked by the BBC’s Laura Kuenssberg whether Sir Keir should quit, Fire Brigades Union (FBU) general secretary Steve Wright said: “Everybody’s thinking it.”
He joined a growing number of Labour peers and MPs who believe the PM’s position is “untenable”.
He noted that senior figures such as the current deputy prime minister David Lammy, who was foreign secretary at the time of the appointment, and his predecessor as DPM Angela Rayner, have said they advised against appointing Mandelson at the time.
Mr Wright said: “Unfortunately we’re seeing MPs being wheeled out again today to sweep up the mess behind the prime minister at the moment.
“I want to see the change that was promised and that this country needs.”






