New tranche of Mandelson papers set to be published before Christmas

New files concerning Lord Peter Mandelson’s appointment as UK ambassador to the US are expected to be made public before Christmas.

A parliamentary vote in February using a "humble address" motion has already forced the release of over 1,500 pages.

However, several documents were initially withheld to avoid prejudicing a Metropolitan Police probe into allegations of misconduct in public office.

Addressing the issue on Thursday, Cat Little, permanent secretary to the Cabinet Office, stated that a portion of these withheld files "can now be published without prejudicing their investigation".

She added she "anticipates that this process will be completed before the House rises for Christmas recess" on December 17.

In a letter to Lord Beamish, the Labour peer who chairs Parliament’s Intelligence and Security Committee (ISC), Ms Little wrote: “I am writing to confirm that the Cabinet Office has been informed by the Metropolitan Police of their assessment that a number of these documents can be published without prejudicing their investigation.

“The Cabinet Office is now beginning the process to prepare these documents so that they may be laid before the House in response to the humble address motion as soon as possible.

“I anticipate that this process will be completed before the House rises for Christmas recess.”

Ms Little wrote that the documents will need to be reviewed “to assess whether or not they may require redactions for the purposes of avoiding prejudice to national security or international relations, and therefore referral to the ISC”.

Members of the ISC will be able to see the unredacted files before they are published more widely, with some information concealed.

Some documents will “continue to be held back at the request of the Metropolitan Police to avoid prejudicing an ongoing investigation”, the permanent secretary said.

These will be published when the Cabinet Office is “able to do so without risk to that investigation or any subsequent legal process”, Ms Little added.

A Met Police spokesperson said: “Our investigation into alleged misconduct in public office is ongoing.”

Lord Mandelson became the UK’s ambassador to Washington in February last year, after his appointment by former prime minister Sir Keir Starmer.

Sir Keir sacked Lord Mandelson in September 2025 after emails leaked which showed the peer sent supportive messages even as Jeffrey Epstein faced jail for sex offences.

In the most recent tranche of documents, released in June, an official involved in security clearance was seen to admit not knowing how an enhanced clearance system, known as Strap, worked.

In an email to Cabinet Office colleagues about what vetting an ennobled peer would require, a member of the department’s Government Security Group suggested he would be “exempt” from some requirements.

But he referred the question to other civil servants, saying: “I must confess to never knowing how Strap works at the best of times, never mind in this scenario!”

In a 2025 message to Cabinet minister Pat McFadden, Lord Mandelson wrote Sir Keir “lacks verve as does the Cabinet as a whole”.

In addition to her letter to Lord Beamish, Ms Little wrote to Conservative MP Simon Hoare, chairman of the Commons Public Administration and Constitutional Affairs Committee, and Labour MP Dame Emily Thornberry, who chairs the Commons Foreign Affairs Committee.