Morgan McSweeney admits he was 'wrong' in advising the Prime Minister to appoint Mandelson
The former aide said he learned details of Mandelson’s relationship with Jeffrey Epstein through released files and said the revelations were "like a knife through my soul"
Morgan McSweeney has admitted he was wrong in advising Sir Keir Starmer to appoint Lord Peter Mandelson as US ambassador to the UK.
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In a statement before his testimony to the Foreign Affairs Committee, Sir Keir Starmer’s former chief of staff said: "The appointment of Mandelson as ambassador was a serious error of judgment".
The comments defending Starmer come hours before the PM will face MPs in the Commons voting on whether the Privileges Committee should consider if he misled the House.
McSweeney told the committee that his recommendation was made based on Mandelson's "experience, relationships and political skills".
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Mandelson was sacked as US ambassador last year because of his links to Epstein, after featuring in documents released by the US Department of Justice related to the paedophile financier.
"I advised the Prime Minister in support of that appointment, and I was wrong to do so," he said.
"As I said in my resignation statement, I resigned because I believe responsibility should rest with those who make serious mistakes.
"Accountability in public life cannot apply only when it is convenient. The Prime Minister relied on my advice, and I got it wrong.
"It is also important, however, to distinguish between what I did do and what I did not do.
"What I did do was make a recommendation based on my judgment that Mandelson’s experience, relationships and political skills could serve the national interest in Washington at an important moment.
"That judgment was a mistake. What I did not do was oversee national security vetting, ask officials to ignore procedures, request that steps should be skipped, or communicate explicitly or implicitly that checks should be cleared at all costs.
"I would never have considered that acceptable. These processes are in place to protect our national security."
McSweeney also admitted that Mandelson may not have been given the role if Kamala Harris had won the US election.
He said: "I think the Prime Minister wanted to rightly wait to see the outcome of that (election). I think if Kamala Harris had won that US presidential election, I don’t think that Peter Mandelson would have necessarily been appointed, and he probably wouldn’t have been.
"I think the Prime Minister started to seriously consider names after the US election."
Last week, Sir Olly Robbins, who was the senior civil servant in the Foreign Office until he was sacked by the PM, told the Foreign Affairs Committee that there was "constant pressure" to approve the appointment.
But he added that this did not affect his decision to give Lord Mandelson security clearance to take up the role.
Speaking on Tuesday, McSweeney also said Starmer considered a "wide range of views" when deciding on the appointment.
He hit out at suggestions by some Cabinet ministers who warned against the decision at the time.
McSweeney admitted he learned details of Mandelson’s relationship with Epstein through the release of files related to the paedophile financier over the course of last year.
He said: "The nature of the relationship that I understood he had with Epstein was not a close friendship. 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, and it was when I saw the pictures, when I saw the Bloomberg questions in September 2025, I have to say it was like a knife through my soul."
Mr McSweeney told the Foreign Affairs Committee: "I have to say, I know that a lot of people now say they told the Prime Minister they were against it at the time.
"Everything I know about how the Prime Minister works is he will consult widely, he will take a lot of views on, and if everybody else was opposed to this appointment but me, he would not have made an appointment such as that.
"He does like to try to build consensus within his team and to get a wide range of views. And he doesn’t just listen to one person on it.
"He certainly spoke to other ministers, other senior staff and took his time reaching decisions he reached."
Asked whether he actively thought the peer could not be granted clearance, McSweeney said: "No. And if it had happened, we’d have withdrawn the ambassadorship.
"It would have been a political embarrassment."
The address came on the same morning that the former chief of the Foreign Office told the Committee that he was told to "get on with" the appointment despite worries about Mandelson's link to Epstein.
Sir Philip Barton told MPs today: "I was presented with a decision and told to get on with it. There was no space for dialogue."
He added: "A decision had been taken. It was a political decision."