Allies of Sir Keir Starmer have issued a stark warning to Labour MPs contemplating a leadership challenge by Angela Rayner, stating that any coup attempt could precipitate a general election.

The Prime Minister is currently navigating turbulent waters, his position in Downing Street under threat due to the fallout from the Lord Mandelson scandal. This controversy has led to murmurs among backbenchers, casting doubt over his political longevity.

In an effort to quell the unrest, Sir Keir has committed to making public documents pertaining to Lord Mandelson’s appointment as the US ambassador in February last year. However, the release of these documents is now under the purview of Parliament’s Intelligence and Security Committee (ISC), which will determine what information is disclosed.

Sir Keir’s decision to relinquish control of the document release came after a significant revolt within the House of Commons, led by none other than Ms. Rayner, the former deputy Prime Minister. This internal rebellion forced him into a policy reversal on Wednesday.

In the aftermath of these events, it has come to light that Ms. Rayner has expressed her readiness to mount a leadership challenge. Despite being embroiled in an ongoing investigation into her tax affairs, she reportedly confided in an MP, saying, “I will be ready.”

The Daily Mail understands that in the wake of Wednesday’s drama, Ms Rayner told an MP ‘I will be ready’ to launch a leadership challenge, despite an ongoing probe into her tax affairs.

It has also been suggested Labour’s ‘women in grey suits’ could be sent to tell Sir Keir that his time is up.

But Sir Keir’s allies are warning that any new PM, such as Ms Rayner, would not have a personal mandate from the electorate and therefore should call a general election.

Sir Keir Starmer’s allies have warned rebel Labour MPs a coup against the Prime Minister by Angela Rayner will trigger a general election

One Labour figure who has served on Sir Keir’s front bench told The Telegraph: ‘Presumably Angela Rayner, if she got elected, would have a completely different agenda. 

‘If you come in with a completely different agenda then the country legitimately says, ‘We didn’t vote for this’.

‘And so what are the grounds for refusing a general election? You can claim constitutional grounds, but in the world of frenzied media, of TikTok, YouTube and GB News, is it really sustainable? It doesn’t feel sustainable to me.’

Speaking about the prospect of a leadership switch, a Cabinet minister supportive of Sir Keir added: ‘The pressure for an election would be enormous.’

It comes amid fears in Government that the release of Lord Mandelson’s emails and messages from his time as US ambassador could lay waste to Sir Keir’s attempts to stay close to Donald Trump.

Officials fear that material published as part of a probe into how Lord Mandelson –  revealed to be a close friend of notorious paedophile Jeffrey Epstein – was hired by the PM could include ‘damaging’ comments made by the former diplomat about the notoriously thin-skinned US President.

One official told Politico that ‘there is lots which could be damaging’, adding that the disgraced former minister and diplomat ‘used to download his thoughts in real time’.

The Epstein files have shown Lord Mandelson sharing lewd and off-the-cuff messages with the late child abuser, including joking about ‘well-hung young men’ when he was a Cabinet minister.

The PM on Thursday said he was ‘sorry for having believed Mandelson’s lies’ and for having appointed him as US ambassador in February 2025.

Sir Keir has promised to release documents related to Lord Mandelson’s appointment as US ambassador in February last year 

The PM on Thursday said he was ‘sorry for having believed Mandelson’s lies’ and for having appointed him as US ambassador in February 2025. 

But Labour grandee Baroness Harriet Harman said it looked ‘weak and naive and gullible’ for Sir Keir to say ‘he lied to me’ and warned the Mandelson scandal would ‘finish him off’ unless he took the right course of action. 

‘He should be reflecting on why he made that appointment,’ she told Sky News’ Electoral Dysfunction podcast.

‘He should also be thinking about a real reset in No10, because what you need from your team in No10 is people who share your values and your principles and who will help you be the best prime minister you can be according to your true self.

‘And clearly that is not what happened because the Keir Starmer who was DPP (director of public prosecutions), would never have appointed somebody like Peter Mandelson to represent the country.’

Leadership speculation intensified on Thursday as the PM gave a speech apologising to Epstein’s victims for believing the peer’s ‘lies’ about his relationship with the paedophile financier.

Backbenchers have called for either the PM’s chief of staff Morgan McSweeney to be sacked or for Sir Keir himself to step down after bombshell revelations about Lord Mandelson’s dealings with the child sex offender.

However, immigration minister Mike Tapp on Friday defended the under-pressure aide in a round of media interviews.

The so-called ‘special relationship’ between the UK and US is already under strain, despite Sir Keir’s best efforts to maintain it.

Trump has levied tariffs on UK-made imports, embarked on a major row with America’s Nato allies and even disparaged British troops who fought and died in Afghanistan. 

The release could be delayed because the Metropolitan Police has asked the Government not to publish documents that would ‘undermine’ its probe into allegations of misconduct in public office.

And the ISC said it could not provide a timetable for releasing the documents as it reviews whether some of the papers should be withheld for national security reasons. 

Labour grandee Baroness Harriet Harman said it looked ‘weak and naive and gullible’ for the PM to say ‘he lied to me’ and warned the scandal would ‘finish him off’

At an emergency press conference in Hastings the rattled-looking PM said he was ‘utterly disgusted’ by revelations about Lord Mandelson’s relationship with Epstein and ‘sorry’ he had appointed him as ambassador to Washington DC. 

But he insisted that he would ‘go on’, despite mounting Labour fury over the fiasco. And Downing Street rejected calls from Labour MPs to sack Mr McSweeney, who championed Mandelson’s appointment.

Seven Labour MPs directly called for Mr McSweeney to go, while numerous others called for a wider No10 clearout – and two said Sir Keir should resign.

One, Simon Opher, said there needs to be a ‘clearout’ of No10.

On BBC Radio 4’s Today programme on Friday, the Labour MP said: ‘There’s a lot of anger amongst Labour MPs, because really we want to, I mean, yesterday, I want to be talking about the cancer care plan, not about Peter Mandelson.

‘So I think what we need to do, I think what needs to really happen is that we need to, Keir Starmer needs to change his advisers in Number 10, I think he’s been badly advised, and he’s been really let down, particularly on this decision.’

Asked whether this meant Mr McSweeney leaving, Mr Opher replied: ‘I think so yes’.

‘If my chief of staff had done this I think he would be looking for another job to be honest,’ he said.

Asked whether the PM had become a ‘drag’ on the Labour Party, Mr Tapp told Sky News: ‘We’re starting to turn the corner.

‘I believe if we stick with Keir Starmer, which we will, then that corner will turn faster and people will start to feel it.

‘But I completely understand the anger and the distress at what’s happened with Peter Mandelson’s appointment.

‘I completely agree with that, and that’s why I’m really pleased to see a genuine, genuine apology from Keir Starmer.’