Sir Philip Barton, the former top civil servant at the Foreign Office, has told MPs he was unable to raise his worries about Lord Mandelson's appointment as UK ambassador to the US.
Testifying before the Foreign Affairs Committee, Sir Philip said he was concerned that the Labour peer's past ties to convicted sex offender Jeffrey Epstein could become a "potentially difficult issue." However, he was "presented with a decision" made by Prime Minister Sir Keir Starmer and "told to get on with it."
"There was no space or avenue or mechanism for me to put that on the table," Sir Philip said.
Lord Mandelson was appointed in December 2024 but was sacked in September 2025 after new details emerged about his friendship with Epstein. Sir Keir has faced ongoing questions about his judgment.
Sir Philip said he was first informed of the decision on 15 December 2024, and was told a due diligence process had been carried out and the prime minister was aware of the risks.
He described No 10's attitude towards vetting as "uninterested" rather than dismissive, citing time pressures to complete the process before Donald Trump's inauguration.
In a separate hearing, former Downing Street chief of staff Morgan McSweeney admitted the appointment was "a serious error of judgment" and apologized to Epstein's victims. He said he had wrongly assumed Lord Mandelson was truthful about his relationship with Epstein.
MPs are set to vote on whether to launch a parliamentary inquiry into claims the prime minister misled Parliament over the vetting process. Sir Keir has denied the accusations.
"The prime minister relied on my advice, and I got it wrong," McSweeney said during his testimony.