Labour MPs have admitted Sir Keir Starmer’s days in Downing Street are numbered as backbenchers turn against the Prime Minister.

Earlier today, the PM backed down from his original plans for top civil servant Sir Chris Wormald to decide which documents relating to the appointment of Peter Mandelson as US Ambassador could be released.

Under pressure from Labour MPs, led by former deputy Prime Minister Angela Rayner, Sir Keir Starmer accepted the decision could be made by Parliament’s Intelligence and Security Committee (ISC) instead.

Sir Keir Starmer will try to move on with a press conference tomorrow, where he will say “Britain has been undermined by political neglect”, announcing £800million in new funding to revamp decrepit high streets is announced.

However, MPs have said the eventual release of the documents, which could be delayed by a police investigation into Mandelson, could launch someone in the party to begin a leadership challenge.

One MP told The Guardian: “Trust is finite. I’m personally not sure I could trust myself to back the prime minister in a confidence vote.”

A former Labour minister added: “We’ve had a lot of bad days recently, but this is the worst yet, I think.”

Another MP who was once an ally of Sir Keir painted a bleak picture of the mood around Westminster among Labour politicians, saying: “You could feel the atmosphere change; it was dark.”

A backbencher called the appointment “indefensible”, adding: “They knew all about Peter’s relationship with Epstein but gave him the job anyway.”

Multiple MPs called on the Prime Minister’s Chief of Staff, Morgan McSweeney, who had been close to Mandelson, should take responsibility for the failures and resign.

One MP said: “The Government is on the run. Goodness knows what will come out, there could be a lot of red faces and departures off the back of it.”

Not every Labour MP was so pessimistic in their outlook.

One suggested that while there was a lot of heat and noise behind the scene, few Labour MPs and no ministers were yet willing to put their heads above the parapet, adding “I think if [Rayner] had said something it would be game over. The PM is safe for now.”

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Sir Keir earlier told the Commons he knew about Mandelson’s ongoing friendship with convicted paedophile Jeffrey Epstein when he appointed him ambassador to the US. However, he said the peer “lied repeatedly” about the extent of the relationship.

Lord Mandelson, a political appointment rather than a career diplomat, was sacked from his Washington role in September last year over his links with Epstein, who died in 2019.

His continued association with Epstein following a 2008 conviction for soliciting a minor had been widely reported before his return to the political front line, when he was named as ambassador in 2024.

But documents released as part of the US Department of Justice’s Epstein Files raised new concerns in recent days.

The Metropolitan Police have meanwhile told the Government not to release “certain documents” that would “undermine” their investigation into the disgraced peer

Minister Chris Ward told the Commons: “I just want to confirm to the house the material will not be released today because of the conversation with the Metropolitan Police over that, but it will be released as quickly as possible, in line with the process set out before the House.”

He said there was “a lot of material” to go through and pointed to other humble addresses that have taken “weeks or months.”

Documents will be released by the Cabinet Secretary working with lawyers or, for material deemed to potentially conflict with national security or foreign relations, it will be passed to the ISC to decide, he said.

Reacting to today’s news in the Commons, former Shadow Chancellor and veteran left-wing MP John McDonnell said: “I’ve never called for him to go, but I have lost confidence in him. I think Keir needs to examine his own situation, certainly his own position.”

Labour MP for Alloa and Grangemouth Brian Leishman admitted some of his fellow backbenchers had “lost confidence” in Mr McSweeney and described his position as “untenable.”

A Downing Street spokesman said: “Peter Mandelson’s actions were unforgivable. He lied to the Prime Minister, hid information that has since come to light and presented Jeffrey Epstein as someone he barely knew.

“We will comply with the motion, including publishing documents relating to Peter Mandelson’s appointment, which will show the lies he told.”