Morgan McSweeney has rejected accusations of bullying civil servants into approving Lord Mandelson's appointment as US ambassador.
Speaking at the Kyiv Security Forum on Thursday, Sir Keir Starmer's former chief of staff acknowledged the decision was "wrong", while distancing himself from characterisations of his conduct.
"I find it strange reading about a character with the same name as mine sometimes. I don't recognise that character," Mr McSweeney told the conference in Ukraine.
The former Downing Street adviser, who stepped down in February over the controversy, faces questions from the foreign affairs committee next week.
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He has been accused of telling officials to "just f***ing approve him" when pushing for the peer's nomination.
"My role was to advise the Prime Minister. I take responsibility in the advice that I gave and resigned," Mr McSweeney stated.
The scandal deepened on Thursday when Cat Little, the Cabinet Office permanent secretary, informed MPs that the Prime Minister's official instruction to proceed with Lord Mandelson's appointment had vanished from government records.
The note, which should have been dated December 18 2024, documented Sir Keir's decision to press ahead despite officials having compiled a detailed due diligence file warning about the peer's business activities and connection to Jeffrey Epstein.
Morgan McSweeney has been accused of telling officials to 'just f***ing approve him' when pushing for Mandelson's nomination
| GETTYWhen Conservative MP Sir John Whittingdale questioned why this document was absent from files released on March 11, Ms Little responded: "There are a number of examples where we have had to undertake further investigation, based on the information that we have."
She confirmed additional searches had been conducted, but offered no explanation for the missing record.
The Prime Minister now faces the prospect of a parliamentary vote to refer him to the privileges committee over allegations he misled the House of Commons.
The Liberal Democrats, SNP and suspended Labour MP Karl Turner have urged Speaker Sir Lindsay Hoyle to schedule such a vote.
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Sir Keir's critics contend he made false statements on two occasions regarding Lord Mandelson's vetting and his assertion that "no pressure existed" to grant security clearance.
The Conservatives are understood to be weighing whether to table a motion demanding an investigation, following Kemi Badenoch's public accusation that the Prime Minister misled MPs.
Senior Cabinet figures including Rachel Reeves, Wes Streeting, Shabana Mahmood and David Lammy also voiced concerns during a Cabinet meeting this week.
Labour MPs Graham Stringer and Jonathan Brash have demanded Sir Keir's resignation.
Lord Mandelson was arrested in February under suspicion of misconduct in public office | GETTYSir Olly Robbins resigned on Thursday after approving Lord Mandelson's security clearance without informing Downing Street about the UK Security Vetting agency's assessment.
The former Foreign Office permanent secretary told MPs on Tuesday that an "atmosphere of pressure" surrounded his department's handling of the appointment.
Documents revealed Sir Olly had sought to arrange an audience between Lord Mandelson and the King before vetting checks were complete.
Messages released ahead of a second tranche of documents showed Sir Keir describing Lord Mandelson as "brilliant" the evening before announcing his ambassadorship.
The Prime Minister expressed enthusiasm about "working side by side" with the peer.
During a visit to the North East on Thursday, Sir Keir declined to confirm his Cabinet remained united behind him.
Boris Johnson faced a similar privileges committee inquiry in 2022 over Covid rule statements, with the committee ultimately finding he had knowingly misled the House.