Dame Emily Thornberry, chairman of the Commons foreign affairs committee, has written to Foreign Secretary Yvette Cooper demanding a full explanation of the vetting process that led to Lord Peter Mandelson's appointment as Britain’s ambassador to the United States.
Thornberry said she had "repeatedly" sought to question Lord Mandelson before his departure for Washington in February but was blocked by the Foreign Office and the then foreign secretary, David Lammy. In a letter to Ms Cooper, who had been in the post for barely a week when she received the correspondence, Thornberry asked what security concerns were raised during vetting, how the Foreign Office responded and whether any concerns represented a "potential barrier" to the appointment or led to conditions being placed on his remit.
"It has been suggested... that security concerns were overlooked... and that such decisions may have been taken by actors outside of the Foreign Office, perhaps senior people in No10," Thornberry wrote. "These allegations are potentially very serious... it is my responsibility to ensure the House of Commons receives a thorough response to a number of important unanswered questions."
Lord Mandelson, who had been appointed by Labour leader Sir Keir Starmer, was removed from the ambassadorial role after the scale of his links to convicted paedophile financier Jeffrey Epstein emerged publicly. The development followed the publication of emails said to show Mandelson had sent supportive messages to Epstein while the financier faced jail for sex offences; Starmer defended the appointment until those messages surfaced.
Downing Street said the prime minister had confidence in the existing vetting system. A No 10 spokesman said: "We always keep national security vetting and other procedures under constant review to make sure they retain their position as world-leading."
Thornberry asked Ms Cooper to clarify whether the Foreign Office considered the vetting concerns to be a potential disqualification and to state whether any limits were set on Mandelson's duties. She also urged a review of pre-appointment scrutiny to prevent "embarrassing diplomatic incidents" in future.
The request adds to pressure on ministers to explain how the appointment proceeded despite reported reservations. The sequence of events — a February departure for Washington, denials of committee access to question the nominee, and the subsequent emergence of the emails that led to Mandelson's removal — has prompted cross-party scrutiny of the processes by which senior diplomatic appointments are cleared.
Thornberry's letter is the latest salvo from within Labour ranks demanding greater transparency over the decision-making around high-profile postings. The Foreign Office and Downing Street have been asked for further comment on the specifics of the vetting record and whether external actors influenced the outcome.