Keir Starmer’s leadership faced increasing challenges today as Angela Rayner emerged as a key figure in a Labour rebellion concerning the alleged cover-up involving Peter Mandelson.

MPs, including the former Deputy Prime Minister, are insisting that the Intelligence and Security Committee of Parliament be given the authority to determine what information should be disclosed about Mandelson’s vetting process prior to his appointment as the US ambassador.

Amidst this turmoil, intense negotiations are underway in the House of Commons between government ministers and backbench MPs, in a bid to avoid a significant defeat on a Conservative-led motion that could severely undermine Sir Keir’s leadership.

In a tense session of Prime Minister’s Questions, Sir Keir sought to regain the initiative by accusing the ex-Cabinet minister of having “betrayed” the nation. He vowed that Mandelson would be legally stripped of his “Lord” title and removed from the Privy Council.

Sir Keir claimed that Mandelson had been deceitful throughout the process of his appointment as an envoy to Washington, promising to release relevant details.

However, for the first time, Sir Keir acknowledged that he was aware of Mandelson’s ongoing association with Jeffrey Epstein, even after Epstein’s initial conviction for sex offenses, at the time of Mandelson’s appointment.

And he claimed some information would have to be withheld for ‘national security’ and ‘international relations’ reasons, as well as to avoid prejudicing a police investigation.

The government has been left floundering after the Tories tabled an ‘humble address’ demanding the publication of a swathe of material about Mandelson.

Ministers tried to neutralise the row with an amendment striking out documents crucial for ‘national security and international relations’, potentially giving ministers a get-out.

During the debate this afternoon, Cabinet Office minister Nick Thomas-Symonds conceded that the ISC could scrutinise the ‘approach’ to making decisions on what could be published. But it was quickly clear that commitment from the despatch box did not go far enough. 

The involvement of Ms Rayner will cause panic in Downing Street, as she is regarded as ‘on manoeuvres’ for the leadership.

There are claims she has secured a £1million warchest for a bid to succeed Sir Keir should the opportunity arise. 

Speaking in the chamber, Ms Rayner pointed to a previous disclosure motion she tabled in 2022.

In it, she said the Commons Public Accounts Committee should look at papers related to personal protective equipment (PPE) contracts.

Ms Rayner asked: ‘Should we not have the ISC not have the same role now in keeping public confidence in the process?’

Mr Thomas-Symonds said MPs were ‘asking, quite fairly, a broader question… about scrutiny’. 

Treasury Committee chair Meg Hillier said: ‘There are well worn filters through parliament… to properly and sensitively handle information which in my time has never leaked.

‘There is consensus that everyone wants as much information in the public domain.’

Veteran Labour MP Clive Efford called for a ‘manuscript amendment’ to spell out the process for deciding what files are released.

There’s clearly concern about the government amendment and that it doesn’t go far enough about the government documents that might be withheld,’ he added.

As pressure built, Mr Thomas-Symonds signalled a concession that the Cabinet Secretary would take avice from an ‘independent’ KC and accept ‘scrutiny of the approach he is taking by the ISC’.

‘I hope that will give the House the reassurance it needs,’ he added.

As he was grilled by Kemi Badenoch at PMQs, Sir Keir argued decisions on what to publish would not be a ‘political process’. 

But the Tory leader insisted there would be a ‘cover up’ to protect ‘the Prime Minister and his chief of staff Morgan McSweeney, a protege of Peter Mandelson’.

‘The Prime Minister chose to inject Mandelson’s poison into the heart of his Government on the advice of Morgan McSweeney,’ she said.

Sir Keir appeared to lash his fate to that of his chief of staff – the subject of much anger from MPs. ‘Morgan McSweeney is an essential part of my team,’ he said. 

Labour MPs are openly saying the tweak is unacceptable this morning, as the government would be able to ‘mark its own homework’. 

The stage is set for a dramatic political showdown after police launched a criminal investigation into allegations Lord Mandelson passed market-sensitive information to Jeffrey Epstein while a Cabinet minister. 

Poland last night launched a probe into whether Epstein was a Russian spy – with British intelligence experts saying it was ‘very likely’ he was sharing compromising material with the KGB.  

Lord Mandelson has denied the huge tranche of evidence released by the US government on Friday shows he broke the law. 

The New Labour architect has stepped down from the Lords as of today, after Sir Keir threatened to pass legislation to kick him out. But he will retain his title unless there is a change in the law, and has insisted his career in public life is not over.

Mrs Badenoch told the House that the decision to appoint Mandelson as US ambassador ‘goes to the very heart of this Prime Minister’s judgment’.

Sir Keir paid tribute to Epstein’s victims and told the Commons: ‘To learn that there was a cabinet minister leaking sensitive information at the height of the response to the 2008 crash is beyond infuriating, and I am as angry as the public and any member of this House – Mandelson betrayed our country, our Parliament and my party.

‘He lied repeatedly to my team when asked about his relationship with Epstein before and during his tenure as ambassador. I regret appointing him.

‘If I knew then what I know now, he would never have been anywhere near Government.

‘That is why, yesterday the Cabinet Secretary, with my support, took the decision to refer material to the police, and there is now a criminal investigation.

‘I have instructed my team to draft legislation to strip Mandelson of his title and wider legislation to remove disgraced peers, and this morning, I have agreed with His Majesty the King that Mandelson should be removed from the list of privy counsellors on grounds that has brought the reputation of the Privy Council into disrepute.’

The PM admitted he knew that Mandelson had continued his friendship with Epstein after the financier was convicted of sexual offences.

But added: ‘What was not known was the depth, the sheer depth and the extent of the relationship. He lied about that to everyone for years, and new information was published in September showing the relationship was materially different from what we’d been led to believe. When the new information came to light, I sacked him.’

Sir Keir said the Government intends to publish all the information it is able to about the due diligence process before Lord Mandelson was appointed ambassador to the US.

However, he suggested that key details will not be released. 

‘So I can be totally open with the House, I should also disclose that the Metropolitan Police have been in touch with my office this morning to raise issues about anything that would prejudice their investigations,’ he said. 

‘We’re in discussion with them about that, and I hope to be able to update the House, but I do think I should make that clear.’

Giving interviews for the government this morning, Cabinet minister Wes Streeting confirmed that papers about Lord Mandelson’s vetting would be published.

He said there was a sense of betrayal about the peer’s actions, saying he did not regard the peer as a friend any more.

He told Times Radio: ‘You can see the outrage across the political spectrum and from people up and down our country.

‘I cannot state strongly enough how bitterly that betrayal feels for those of us in the Labour Party who feel very personally let down and also feel that he, as well as betraying two prime ministers, betraying our country and betraying Epstein’s victims, has fundamentally betrayed our values and the things that motivate us and the things that brought us into politics, which is public service and national interest, not self-service and self-interest.’

Tory leader Kemi Badenoch will look to focus fresh attention on Sir Keir’s move to appoint Lord Mandelson the UK’s ambassador to the US last year.

She demanded Downing Street explain the vetting process as she claimed concerns were ‘waved away’ so that the Prime Minister could make ‘a political appointment of a man who is a close friend of a convicted paedophile’.

Her party will table an humble address motion, an arcane parliamentary mechanism to try to compel the Government to release documents including due diligence work carried out by the Cabinet Office, emails between the PM’s chief of staff Morgan McSweeney and Lord Mandelson relating to his association with Epstein, and minutes of meetings held about the appointment.

Humble addresses, if passed, are binding on ministers.

Mrs Badenoch said she hoped Labour MPs ‘will join us in fighting for the truth’ amid speculation some Labour MPs could abstain amid anger over the affair on the backbenches.

No 10 added an amendment to the humble address calling for all documents to be published saying ‘except papers prejudicial to UK national security or international relations’, according to the Commons order paper.

But Labour MP Andy McDonald told Sky News he would probably still vote with Tories this afternoon.

‘If this amendment were to stand at face value it would be to throw a cloak over the entire Mandelson affair,’ he said.

‘We cannot have the government marking its own homework.’ 

Mr McDonald said the amendment was ‘a nonsense because it just is a way of not revealing information’. 

The Metropolitan Police said last night it had launched a probe into the former government minister for misconduct in public office offences, which carry a maximum sentence of life imprisonment.

The Cabinet Office had passed material to the police after an initial review of documents released by the US Department of Justice as part of the Epstein files found they contained ‘likely market-sensitive information’ and official handling safeguards had been ‘compromised’.

Former prime minister Mr Brown also said he had provided the Met with ‘relevant’ information relating to Lord Mandelson’s ‘inexcusable and unpatriotic act’.

Newly released emails from 2009 appear to show Lord Mandelson share sensitive information on at least four occasions, including an assessment by Mr Brown’s adviser of potential policy measures including an ‘asset sales plan’.

Mr Brown also appeared to suggest that Cabinet Secretary Sir Chris Wormald had not heeded his request last September to examine communication between Lord Mandelson and Epstein.

The Prime Minister’s official spokesman told reporters Mr Brown’s letter to Sir Chris had asked specifically about the sale of Royal Bank of Scotland assets to JP Morgan, and that the Cabinet Secretary had responded in November to say no files were found linking Epstein to the sale.

A Government spokesman said: ‘The Government stands ready to provide whatever support and assistance the police need.’