Sir Keir Starmer must take responsibility for the Peter Mandelson vetting scandal, Rishi Sunak has warned, arguing his appointment as US ambassador was a "grave lapse of political judgment”.

Writing in The Times , the former prime minister said the government is “at risk of learning the wrong lessons from this sorry episode”, arguing that it was "not a failure of process but of political judgment”.

In his first intervention on the issue, the MP for Richmond said: "I fear, though, that we are at risk of learning the wrong lessons from this sorry episode. A view is taking shape that we need yet more process. Already, we have a review by a retired judge into security vetting.

Rishi Sunak said the government ‘is at risk of learning the wrong lessons’ from the Mandelson scandal (AFP/Getty)

"The temptation for Downing Street will be to announce a new set of processes and claim that these mean this mistake could not happen again. The government will hope it will be a chance to move on from this scandal.…