Joe Pike,Politics investigations correspondentand
George Wright
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The second tranche of documents relating to Lord Mandelson's appointment as the UK's ambassador to the US will be published on Monday, three sources involved in the process have told the BBC.
While Number 10 has refused to confirm the publication date, a government spokesperson said the latest batch "will be among the largest publications ever laid in Parliament".
Lord Mandelson was sacked as ambassador last year after the emergence of new revelations about the extent of his relationship with the late convicted sex offender Jeffrey Epstein.
In February, MPs voted to force the government to publish all papers relating to the appointment through a humble address, a parliamentary process.
The government initially opposed the motion, arguing that it did not want to publish material that could damage national security or diplomatic relations.
But in a last-minute compromise, the government agreed to first send sensitive documents to the Intelligence and Security Committee (ISC), which would decide what could and could not be published.
The first tranche of documents was published in March.
They showed Prime Minister Sir Keir Starmer was advised that Lord Mandelson's relationship with Epstein posed a "general reputational risk" ahead of his confirmation as US ambassador.
Sir Keir's national security adviser, Jonathan Powell, also said he found the appointment of Lord Mandelson "weirdly rushed".
The government spokesperson said they were "committed to complying with the Humble Address in full", adding: "That reflects the transparent and thorough process we have followed."
The release of the documents comes as parliament returns on Monday after a week's recess.
The government has insisted that all relevant documents will be published, except if the Metropolitan Police has requested any be held back while they conduct their investigation.
Lord Mandelson's vetting file will not be included. It understood the Met Police have asked for it to be held back while they investigate him on suspicion of misconduct in public office. He has denied wrongdoing.
Some documents will be redacted on national security or international relations grounds, or to remove the names of junior officials.
Sir Keir announced he would be appointing Lord Mandelson to the Washington position in December 2024, saying he would bring "unrivalled experience to the role".
However, nine months later Lord Mandelson was sacked after further revelations came to light about his long-standing friendship with Epstein.
Lord Mandelson has said his friendship with Epstein was a "terrible mistake" but insisted he "never saw anything in [Epstein's] life... that would give me any reason to suspect what this evil monster was doing".
MPs from across the parties have been highly critical of the prime minister's decision to give Lord Mandelson the job.
The peer is under criminal investigation over allegations of misconduct in public office and has repeatedly let it be known that he believes he has not acted criminally, did not act for personal gain and is co-operating with the police.