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Sir Keir Starmer has been accused of misleading parliament after it emerged that Lord Peter Mandelson was made Britain’s ambassador to the US despite having failed to clear security vetting.
But Downing Street on Thursday claimed that neither Starmer nor any government minister knew that Mandelson had failed the vetting process, putting the blame on Foreign, Commonwealth and Development Office officials.
The Number 10 line leaves huge questions about the vetting process and Sir Olly Robbins, who had just taken over as the top civil servant at the FCDO when the vetting took place.
Mandelson, a New Labour grandee, had been announced as the prime minister’s choice as ambassador in December 2024, before the usual security checks had taken place.
His “developed vetting” — the secret background checks carried out by security officials at UK Security Vetting, a division of the Cabinet Office — took place in January 2025.
UKSV, whose judgments are nonbinding but almost always followed by departments, advised against granting Mandelson clearance. The Foreign Office overrode that recommendation and the appointment went ahead.
“Neither the prime minister nor any government minister was aware that Peter Mandelson was granted developed vetting against the advice of UK Security Vetting until earlier this week,” a government spokesman said.
The failed vetting was first reported by the Guardian. A person close to Mandelson said that the former ambassador had absolutely no previous knowledge of the matter.
Starmer now faces questions over why he previously claimed that the vetting process had given Mandelson “clearance for the role”. He told parliament three times last September that “full due process” was followed.
“If he has misled parliament, as it looks like he has, he should resign,” said Kemi Badenoch, the Conservative leader.
Sir Ed Davey, leader of the Liberal Democrats, said that if the prime minister had misled parliament, “he must go”.
Reform UK and the Greens both called for Starmer to resign.
One ally of Starmer said it was “inconceivable” that the prime minister would have gone ahead with the appointment if he had been told about any vetting failure. “If he had known this, he would have pulled the appointment.”
Mandelson only spent seven months as ambassador before he was sacked last September over his long-lasting friendship with convicted sex offender Jeffrey Epstein.
In February, police launched a criminal investigation into the former ambassador over possible misconduct in public office. US files suggested that as business secretary more than 15 years ago he had passed confidential UK state information to Epstein, from whom he had previously taken large sums of money. Mandelson has denied any recollection of receiving such payments.
Mike Clancy, general secretary of Prospect, the trade union which represents vetting officers at UKSV, said it was “deeply unfortunate” that Downing Street had “allowed the impression to circulate that the vetting of Peter Mandelson had not been done correctly”.
Information about the security vetting came to light, as officials reviewed documents about Mandelson’s appointment, whose release has been ordered by the MPs.
The government has already released an initial cache of 147 documents, none of which mention the failed vetting.
Documents can be withheld for national security reasons. Officials are now mulling whether that would include some documents that would show Mandelson’s failed vetting.
The government spokesperson said any documents about the vetting would be provided to parliament’s cross-party intelligence and security committee. The committee can challenge any decision to withhold documents.
Mandelson’s ties to Epstein and his two resignations from Sir Tony Blair’s government were described as evidence of “general reputational risk” in a separate due diligence assessment prepared for Starmer.
Those checks flagged that Mandelson had continued his relationship with Epstein after the financier’s conviction for soliciting sex from a minor.
Robbins was appointed permanent secretary in the Foreign Office in January 2025. The foreign secretary was David Lammy, who is now the deputy prime minister.
Starmer said in February this year that Mandelson had gone through “security vetting, carried out independently by the security services, which is an intensive exercise that gave him [Mandelson] clearance for the role. You have to go through that before you take up the post”.
He added: “Clearly both the due diligence and the security vetting need to be looked at again.”
Last September, Lammy’s successor as foreign secretary, Yvette Cooper, and Robbins sent a letter to the foreign affairs select committee that claimed that the vetting had been carried out to the “usual standard” by UKSV.
The pair said the process had “concluded with DV clearance being granted by the FCDO in advance of Lord Mandelson taking up post in February”. They made no mention of the fact that UKSV had opposed Mandelson’s clearance.