In February, the prime minister apologised to victims of the late sex offender Jeffrey Epstein, saying he had “believed (Peter) Mandelson’s lies” before making him Britain’s ambassador to the US. By March, that account had shifted. Faced with evidence that he was warned the appointment posed a “reputational risk”, but gave the peer the job anyway, Sir Keir Starmer accepted on a trip to Belfast that he “made a mistake”.

On Thursday responsibility appears to have moved again – this time on to officials. Sir Olly Robbins, the top civil servant in the Foreign Office, was forced out after the Guardian reported that Lord Mandelson had been denied security clearance for the role. No 10 said it was not told. These are not complementary explanations. They are competing ones. Either Sir Keir was misled, ignored warnings, or was failed by the system.

The government’s account of the vetting process is in doubt. Ministers say warnings were overridden. But experts say that’s not how it works. Ministers hear the outcome, not the underlying intelligence – making scrutiny difficult once a decision is set, and increasing the risk that conclusions align with it, as in Mandelson’s case. Hence, blaming Sir Olly for failing to share the intelligence looks like justification after the fact. The risks attached to giving Lord Mandelson such a sensitive job were not only in classified files; they were also in the public domain or available to Sir Keir.

By endorsing Lord Mandelson’s appointment in advance, Sir Keir seems to have made the vetting process about delivery not scrutiny. In those circumstances, problems don’t get raised. They get buried by a system in which inconvenient facts cannot reach the top. That’s why “I did not know” is not a valid defence. Ministers are responsible not just for what they’re told, but for whether anyone can tell them the truth. Saying that the announcement was necessary before security vetting took place because the US had to approve of Lord Mandelson’s appointment is an attempt to move away from the real issue: was it safe or appropriate for Britain to make Lord Mandelson ambassador? The answer was – and remains – no.

The cardinal rule of British politics is never to lie to parliament. Sir Keir has hidden behind the language of process. Tory leader Kemi Badenoch has not always shone in the Commons. But in February this year she directly asked Sir Keir whether “the official security vetting mention(ed) Mandelson’s ongoing relationship with the paedophile Jeffrey Epstein?” The prime minister said: “Yes, it did.” Perhaps he confused vetting with due diligence. But if he now says he didn’t know, why did he say he did?

Civil servants warned No 10 in December 2024 of the risks of making Lord Mandelson the US ambassador because he continued his “relationship” with Epstein even after the financier was convicted in 2008 for child sex offences. That was not information discovered after the fact. It was part of the advice available before his appointment. Sir Keir has not told MPs whether his “mistake” was appointing Lord Mandelson without knowing the risks, or appointing him despite knowing them.

The prime minister expects to come to parliament to correct the record and avoid being held in contempt – a verdict which did for Boris Johnson. Labour MPs may want to keep him rather than court instability. With May’s local elections looming, backbenchers might think that unity matters more than accountability. If so, it is a decision that they may come to rue.

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