Keir Starmer will face a vote on whether to launch an investigation into claims he misled the Commons over his decision to appoint Peter Mandelson as ambassador to Washington.
Sources have told the Guardian that the speaker, Lindsay Hoyle, is expected to allow a debate on Tuesday on potentially referring the prime minister to the privileges committee.
The vote is the latest test of Starmer’s authority, which has been damaged by the Guardian’s revelation that Mandelson was installed as ambassador despite the advice of vetting officials that he be denied security clearance.
The Tories have accused the prime minister of misleading the house when he said “full due process” had been followed during the appointment process. Misleading parliament is considered a resigning offence for ministers, and a privileges committee investigation in 2023 prompted Boris Johnson’s resignation as an MP.
The government is likely to whip Labour MPs to vote against an investigation, making it unlikely the Conservatives will succeed. However, some Labour MPs may side with the opposition, giving a sense of the party’s discontent with the prime minister over the issue.