Morgan McSweeney has said he "regrets" not asking the Cabinet Office’s propriety and ethics team to ask Peter Mandelson follow-up questions about his relationship with Jeffrey Epstein as part of the due diligence process for the appointment to the US ambassador position.
Appearing before the Foreign Affairs Committee today, the former chief of staff to the prime minister Keir Starmer was asked about his role in the appointment, including his questioning of Mandelson as part of due diligence checks.
When the due diligence process carried out by the Cabinet Office's Propriety and Ethics Team prior to Mandelson’s appointment brought up questions about Mandelson’s relationship with Epstein, McSweeney and the then-comms chief to the PM Matthew Doyle both wrote to Mandelson with follow-up questions.
Asked by FAC chair Emily Thornberry if this was appropriate, McSweeney: "When I look back on it, I certainly think it would have been much, much better if I’d asked PET to ask those follow up questions.
He added: “I guess my thinking at the time was if I put follow-up questions to him in writing, and that if a senior member of staff did that, that he would feel more obligated to give the truth and the full truth.
“Also thought if I was wrong and he had been lying that might be picked up with DV.”
Mandelson was announced as ambassador to the US in December 2024 and took up post in Februrary 2025 following a security vetting process. McSweeney resigned in February 2026 over his role in Mandelson's appointment as ambassador to the US.
At the beginning of the session, McSweeney said: “The appointment of Manderson as ambassador was a serious error of judgment. I advised the prime minister in support of that appointment and I was wrong to do so.
“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.”
McSweeney said he believes that Mandelson put himself forward for the job and also confirmed that George Osborne was the other candidate who was considered by the prime minister for the ambassador to the US role.
McSweeney said he considered Mandelson to be the "lead candidate" because of "his experience as an EU trade commissioner and the political skills that I thought he could bring to the table".
He also said that it is unlikely Mandelson would have been appointed if Kamala Harris had won the US presidential election rather than Donald Trump.
McSweeney was being questioned as part of oral evidence sessions the Foreign Affairs Committee launched last week after Foreign, Commonwealth and Development Office permanent secretary Sir Olly Robbins was sacked from his job in an ongoing row over the security vetting process for the Mandelson appointment.
Robbins gave evidence last week, with Robbins's predecessor Philip Barton giving evidence this morning, followed by McSweeney.
At the McSweeney session, the former chief of staff was asked about comments from Robbins last week that there was an “atmosphere of pressure” surrounding Mandelson’s appointment, with regular phone calls from the No.10 private office to chase up the process, and a "dismissive" attitude to vetting clearance from the centre.
McSweeney said: "I think it’s important that we unpack this idea of pressure because there’s been a lot of conversation about it. There’s pressure in government every day, and most that pressure comes from within.
"Every civil servant, minister, [the staff] I worked with, woke up every morning feeling pressure to make the country better, wanting to move faster - that’s where the pressure comes from. And No.10’s job in all of this is to make sure that the prime minister’s decisions are acted on quickly."
Sweeney said there is a “real difference” between this and “asking people to lower standards".
He added that he "at no point" did he witness anyone in No.10 being "dismissive" about developed vetting or national security.