PM's ex-chief of staff admits 'serious mistake' over Mandelson US ambassador appointment

Morgan McSweeney, who resigned in February over the advice, said he felt the peer's experience as an EU trade envoy would help the UK secure a US trade deal. However, he told MPs on the Foreign Affairs Committee that after fresh revelations about Lord Mandelson's friendship with the late convicted sex offender Jeffrey Epstein emerged it "dawned" on him that the peer had not given the "full truth" about their friendship.

McSweeney admitted No 10 wanted Lord Mandelson in post "quickly" but insisted officials were never asked to "skip steps". In a rare public appearance by a senior advisor, he also denied telling the Foreign Office "explicitly or implicitly" that security checks "should be cleared at all costs".

The decision to appoint Lord Mandelson has dogged the prime minister for months but anger was reignited over the issue after it emerged he was given security clearance for the role by the Foreign Office, despite concerns being raised by vetting officials. The prime minister has said no one in Downing Street - including himself and McSweeney - were aware the Foreign Office had gone against the vetting recommendation until recently.

Sir Keir is facing a vote by MPs later on whether there should be a parliamentary investigation over claims he misled the House of Commons about Lord Mandelson's vetting. While he is unlikely to lose the vote, any rebellion by Labour MPs would do more damage to his authority.

Lord Mandelson was sacked as ambassador in September 2025, after new information came to light about the depth of his relationship with Epstein. This included photos of the pair together and supportive emails he sent to Epstein as he faced charges for sex offences in 2008.

McSweeney told the committee that when he saw the revelations "it was like a knife through my soul". "The nature of the relationship that I understood he had with Epstein was not a close friendship," he said. "How I understood it at the time was a passing acquaintance that he regretted having and that he apologised for.

"What has emerged since then was way, way, way worse than I had expected at the time [of the appointment]."

Before Lord Mandelson was appointed, a due diligence check - a separate process to the security vetting - was carried out by a team at the Cabinet Office and sent to the prime minister. This flagged Lord Mandelson's continued relationship with Epstein after his conviction as a potential "reputational risk".

McSweeney was subsequently asked by the PM to send three follow-up questions to Lord Mandelson about his association with Epstein. While at the time McSweeney said he believed the answers were truthful, he later realised he was not given the "full truth" and that revelations in the Epstein files showed Lord Mandelson was "unfit" for the job.

Challenged over whether it was appropriate for him to ask the follow-up questions, given he was a friend of Lord Mandelson, McSweeney acknowledged that in hindsight it would have been "much better" for "public appearances" if the Cabinet Office's propriety and ethics team had done this. However, McSweeney added that he was not sure the Cabinet Office "would have got better answers".

Earlier, Sir Philip Barton, the top civil servant at the Foreign Office at the time, told the committee Downing Street had been "uninterested" in the vetting process and the focus was on making sure Lord Mandelson was able to start his job by the time of Donald Trump's inauguration. This backed up the account of his successor, Sir Olly Robbins, that there was "pressure" from Downing Street to complete vetting quickly and that No 10 had been "dismissive" about the process. However, Sir Philip denied that this affected the substance of the vetting case.

In response to the claims, McSweeney acknowledged that the PM's private office would have chased the Foreign Office for updates on Lord Mandelson's vetting. He added that Downing Street wanted the process completed "quickly" so Lord Mandelson was in post by the time of Trump's inauguration. However, he insisted nobody was asked to "skip steps" in any part of the process.

"Yes we wanted it done quickly but at no point did I witness anyone being dismissive about DV [developed vetting] or national security," he added.

McSweeney denied reports he had sworn at the top civil servant at the Foreign Office while asking him to approve the appointment. Sir Philip also said he had no recollection of being sworn at by McSweeney.

While he was a key figure in Sir Keir's rise to power and within the Number 10 operation, McSweeney was rarely seen in public and had not spoken about his role in Lord Mandelson's appointment since his resignation statement.

McSweeney denied accusations he had tried to push through the appointment of the former Labour minister and closed his eyes to the risks because he was a friend and his "hero". He insisted he believed he was acting in the "national interest", adding: "This was not some hero I was trying to get a job for."