PRIME Minister Sir Keir Starmer is staring down the barrel of a major Labour rebellion this evening as back-bench MPs have come out against his plan to block a probe into his handling of the Mandelson scandal.

One warned that the cover-up could further erode “the already fragile fabric of our democracy.”

They are refusing to back his demand that they oppose a Tory motion urging that statements by the Prime Minister be scrutinised by the Commons privileges committee.

The committee, which examined Boris Johnson’s lies over “partygate” back in 2022, was proposed to consider Sir Keir’s repeated claims that “full due process” was followed over the appointment of Lord Peter Mandelson as ambassador to Washington.

The row came as the Prime Minister’s former top henchman Morgan McSweeney melodramatically — and implausibly — told a committee of MPs that revelations of the disgraced peer’s relationship with paedophile financier Jeffrey Epstein had been “a knife through my soul.”

In much-anticipated evidence to the Commons foreign affairs committee, Mr McSweeney conceded that he had made a “serious mistake” in pushing for the Mandelson appointment, while denying that the New Labour grandee was a “mentor” or a “hero” to him.

Instead, he tried to play down Lord Mandelson’s importance in Sir Keir’s leadership and Mr McSweeney’s own rise, asserting that the sinister spin-doctor had played no part in Labour candidate selections nor the ill-starred government reshuffle last autumn, as has been reported.

However, the sacked Downing Street chief of staff struggled to explain No 10’s manoeuvres to get Sir Keir’s director of communications Lord Matthew Doyle, a top post in the diplomatic service.

In the end, Lord Doyle had to make do with a peerage and is presently suspended from the Labour Party since he, too, had publicly associated with someone facing child sex abuse charges.

But rather half-hearted and indolent questioning from MPs on the committee largely allowed Mr McSweeney to retreat back into his preferred shadows without further damage to his already-tattered reputation.

No such luck attended Sir Keir on the Commons floor. The tone was set by South Shields MP Emma Lewell, who mounted a coruscating attack on Downing Street’s judgment and its determination to block any reference to the privileges committee.

Her voice shaking with emotion, she told MPs: “Like the public, I feel let down, disappointed and I am angry. 

“Peter Mandelson should never have been appointed. This was a fundamental failure of judgment. Matthew Doyle should never have been given a peerage — this was also a failure of judgment.

“I feel the way that today’s vote has been handled by the government smacks, once again, of being out of touch and disconnected from the public mood.

“That MPs like me are being whipped into voting against this motion is wrong,” she added, and “played into the terrible narrative that there is something to hide and good, decent colleagues will be accused of being complicit in a cover-up.

“Trust has gone and it has been replaced by anger. The already fragile fabric of our democracy is eroding further every day this continues.”

Left MPs John McDonnell and Andy McDonald both intervened in the Commons to argue that the Prime Minister should embrace the scrutiny if he had nothing to hide.

Grangemouth MP Brian Leishman said he would back the motion moved by Tory leader Kemi Badenoch. 

He said: “The Prime Minister should refer himself to the privileges committee. It would say to Parliament — and, more importantly, to the country — that he’s got nothing to hide, and importantly, that transparency and accountability are really at the heart of our democracy.

“The Prime Minister needs to stop putting Labour MPs in awkward situations. The open and honest thing would be to refer himself to the committee but if he won’t then I’m afraid he has left me with no choice. I will have to vote for this motion this afternoon.”

And in a statement Clapham and Brixton MP Bell Ribeiro-Addy said: “I am not in Parliament for today’s vote on referring Keir Starmer.

“If I was, I would be voting for the motion. Transparency is a cornerstone of our democracy.”

One Labour MP told the Star that every local candidate and party officer in his constituency had begged him not to oppose the motion for fear of the damage it would do the party.

MPs were due to vote as the Star published this story, with estimates that up to 30 could rebel, enough to embarrass but not overturn the beleaguered premier.