Last week, Mandelson was “withdrawn” from his role as lead UK diplomat to the US after further details emerged of his relationship with the late convicted paedophile Jeffrey Epstein.

On Sunday, Business Secretary Peter Kyle refused to give any details on whether or not he believed Mandelson had misled the Prime Minister’s office and defended Starmer’s judgment. He said it was “worth the risk” as Mandelson has “outstanding, singular talents”.

However, many MPs reportedly do not share Kyle’s loyalty to Starmer, as the Guardian reports that the Mandelson saga is the latest in a long line of mistakes laid at the Prime Minister’s door.

From the bid to cut winter fuel payments, and subsequent U-turn, the row over freebies he received from Labour donor Lord Alli, and the disastrous bid to cut welfare payments, particularly for the disabled. Mandelson’s sacking, shortly after Angela Rayner's resignation from Government over her tax affairs, is the latest in a long line of disasters that have reportedly shifted the mood amongst Labour MPs.

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Andy Burnham, the Manchester Mayor, has been repeatedly touted as topping the list to replace Starmer over the weekend, with many suggesting he could enter parliament through a by-election.

However, Starmer’s judgement, and that of his chief of staff Morgan McSweeney, are now being intensely questioned. Several MPs have also spoken about their disquiet publicly, highlighting that Starmer could be facing a rebellion.

Backbench MP Clive Lewis told the BBC last week that the prime minister does not seem “up to the job”, while Barry Gardiner said there is a “toxic” resentment fostering among that party’s MPs.

Lucy Powell (below), who was sacked as leader of the house during Starmer’s reshuffle, called for a change of culture. Powell is now one of two candidates to take Rayner’s place as deputy leader.

“We’ve got a bit of a groupthink happening at the top, that culture of not being receptive to interrogation, not being receptive to differing views,” she said.

Powell is one of two contenders for the deputy leadership(Image: Lucy North/PA Wire)

The Guardian reports that MPs are mulling over whether Starmer is up to the job of finding solutions to the country’s problems, with many concluding that he is not. The newspaper suggests that internal grumbling is more than just gossip, and that plans to oust Starmer as prime minister are already in place.

“The conversation has moved on from ‘if’. Now it’s about ‘who’ and ‘how’,” one MP understood to be involved in plotting told the Guardian.

They said Reform UK being given the space to shape the narrative over the summer, while the Government remained quiet, showed there was a need for change. “Before then, there were quite a lot of people saying we’ve got to make it work. We came back after the summer, the mood had significantly hardened,” one MP said.

“People in their constituencies have been getting terrible feedback. Farage has been everywhere. The mood was: this has been a f*****g disaster.

“We’ve been given nothing to do. The government just cleared the pitch.”

Elections in May next year, in Scotland, Wales and local authorities in England, could be a perilous moment for Starmer, but many believe he won’t even survive that long.

The Mandelson row, and Number 10’s slow response to it, has seen furious MPs turn on McSweeney.

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One Blair-era cabinet minister said they were unsure if Starmer would survive until May as the “mood is dire”. They said: “The message from pretty much across the board was that one more major issue like Rayner/Peter and the dam would burst. But this is the Labour party so we shall see.”

Unlike the Tories there is no 1922 backbench committee to write to to remove a party leader, or a device to prompt a confidence vote.

A leader might be expected to do the honourable thing and resign if a vote of confidence is called and carried, but Jeremy Corbyn did not do so when 80% of his MPs did not back him during his time in charge.

The newspaper added that while many feel Starmer should go, there is no “perfect candidate” in the current Cabinet who could be widely seen to replace him, particularly with Rayner now on the backbenches.