FORMER UK AMBASSADOR to Washington Peter Mandelson will quit the House of Lords today after a criminal investigation was launched against him following allegations he passed confidential information to the late sex offender Jeffrey Epstein.

Backlash to the latest release of millions of files relating to Epstein led to Mandelson resigning from the House of Lords yesterday.

British prime minister Keir Starmer’s appointment of Mandelson as ambassador to the United States is now coming under growing scrutiny.

The Conservatives will seek to force the government to release all papers relating to how Mandelson got the Washington job as Starmer faces MPs for Prime Minister’s Questions.

The Metropolitan Police on Tuesday evening said 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 investigation relates to allegations Mandelson passed market-sensitive information to Epstein while serving in Gordon Brown’s Labour administration as it dealt with the fallout from the 2008 financial crash.

Tory leader Kemi Badenoch demanded Downing Street explain the vetting process behind Starmer’s move to appoint Mandelson the UK’s ambassador to the US last year.

She claimed concerns were “waved away” so that Starmer could make “a political appointment of a man who is a close friend of a convicted paedophile”.

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

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 back benches.

Downing Street 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.

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 Gordon Brown also said he had provided the Met with “relevant” information relating to Mandelson’s “inexcusable and unpatriotic act”.

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

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

Starmer’s official spokesman told reporters Brown’s letter to Wormald 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 spokesperson said: “The Government stands ready to provide whatever support and assistance the police need.”

Before Mandelson’s departure from the upper chamber was announced, Starmer had threatened legislation within weeks to strip him of his title and told Cabinet the former business secretary had “let his country down”.

Mandelson has been approached for comment and while he has yet to speak publicly, the BBC said it understood he maintains he did not act criminally and that his actions were not for personal gain.

The BBC reported Mandelson argues he sought Epstein’s expertise in the national interest ahead of the financial crisis.

Meanwhile, Andrew Mountbatten-Windsor has moved from Royal Lodge in Windsor to a property on the King’s Sandringham estate, the Press Association understands.

It comes as police said they were assessing allegations that a woman was sent to the UK by Epstein for a sexual encounter with Andrew.

With additional reporting from Press Association.