Robbins also told the foreign affairs select committee on Tuesday that Downing Street had instructed him to find a senior diplomatic posting for Matthew Doyle, Starmer's then director of communications, and had explicitly ordered him not to inform Foreign Secretary David Lammy of those discussions. Robbins said he felt "quite uncomfortable" with the request and repeatedly warned that such a placement would be "hard to defend," while describing it as part of broader pressure from the top of the government to install senior political figures in senior diplomatic roles. Doyle was later suspended as a Labour peer after it emerged he had campaigned on behalf of a friend charged with possessing indecent images of children.

Starmer pointedly named Oliver "Olly" Robbins, the former permanent secretary of the Foreign Office who stepped down last week, as the official responsible for the decision to overrule the UK Security Vetting agency's recommendation against Mandelson's appointment. Starmer told MPs the withholding of that information was not an oversight but "a decision, repeated on several occasions, not to share that information" with senior ministers. Despite the increasingly personal tone of his Commons statement, Starmer stopped short of admitting he had inadvertently misled parliament — an omission that drew notice given his own past prosecution of Boris Johnson for misleading the House over partygate. Resignation calls mounted throughout the session, but Starmer flatly rejected them.

Addressing the Commons directly, Starmer stripped the Foreign Office of its power to overrule security vetting decisions and announced an investigation into any security concerns arising from Mandelson's tenure as ambassador. Starmer told MPs he would not have proceeded with the appointment had he been informed of the failed vetting, and said he was "furious" that Foreign Office officials had withheld the information from senior ministers. He acknowledged that many members would find it "incredible" that he and other ministers had been kept in the dark, adding: "They are right."

Scotland Secretary Douglas Alexander, dispatched by Downing Street for Monday's morning broadcast round, said the Mandelson appointment was a mistake and that Starmer had already admitted as much and apologised, but maintained the prime minister did not lie because he was never informed that vetting agencies had raised concerns. Alexander acknowledged that existing protocol allowed ambassadors to be publicly named before deep security vetting was completed, but said that process would now change, with vetting required before any appointment announcement is made. Asked directly whether Starmer would lead Labour into the next general election, Alexander said: "I expect so. I think he will, and I think he should" — while noting that "there are no certainties."