Sir Keir Starmer is facing a vote by MPs on whether there should be a parliamentary investigation over his claims about the vetting of Lord Mandelson.

Commons Speaker Sir Lindsay Hoyle said he was allowing a debate on the matter on Tuesday and it would then be up to MPs to decide if the Privileges Committee should hold an inquiry.

The prime minister has denied accusations he misled MPs over whether Lord Mandelson's vetting to be the UK's ambassador to the US followed "due process" and over his assertion that "no pressure whatsoever" was applied to officials at the Foreign Office.

Sir Keir branded the move a "stunt" by the Conservatives and hinted he could order Labour MPs to vote against.

Addressing a meeting of the Parliamentary Labour Party on Monday evening, Sir Keir also told his MPs: "Tomorrow is pure politics and we need to stand together against it."

The BBC understands Labour MPs are likely to be whipped to vote down the Conservative motion to refer him to the Privileges Committee rather than being given a free vote.

Conservative leader Kemi Badenoch said Sir Keir had misled Parliament "multiple times" on the subject.

She urged Labour MPs to "look into their consciences" and back an inquiry by the Privileges Committee.

A Downing Street spokesperson said the claims from the Conservatives "have no substance" and the government is "engaging with the two parliamentary processes that are already running" on Lord Mandelson's appointment "with full transparency".

These include: the requirement to publish documents related to Lord Mandelson's appointment through a procedure known as a humble address; and the Foreign Affairs Committee holding evidence sessions to assess the vetting process.

On Monday, the government published a letter from September 2025 in which the then-head of the Civil Service Sir Chris Wormald told the prime minister that "appropriate processes" were followed in the appointment.

Written evidence from the Foreign Office done in consultation with Ian Collard, the civil servant who was head of security in the department, was also published on Monday by the Foreign Affairs Committee.

It noted that Collard "felt pressure to deliver a rapid outcome" on Lord Mandelson's vetting clearance due to "regular contact from No 10" to the office of the department's permanent under-secretary.

It added Collard "did not personally speak to colleagues in No 10" and he "does not assess that this pressure influenced the professional judgement that was reached by himself or his team".

Labour has a majority in the House of Commons, so a large number of its backbench MPs would have to vote for an inquiry or abstain in order for one to be launched.

The BBC has been told that cabinet ministers have been ringing round Labour MPs to convince them to back the prime minister and vote against referring the matter to the Privileges Committee.

The committee can look into cases of MPs breaking parliamentary rules and in 2023 it ruled that the former Prime Minister Boris Johnson had misled MPs about parties in Downing Street during Covid.

The Ministerial Code states that ministers who knowingly mislead Parliament are expected to resign, while any inadvertent error should be corrected "at the earliest opportunity".

At the start of parliamentary business on Monday, Sir Lindsay said "numerous" MPs, including the Conservative leader, had asked him to allow a vote on holding an inquiry.

He emphasised that his role was "as a gatekeeper" to ensure such votes were held "sparingly" and that he was not taking a view on the rights and wrongs of the case.

The order paper published ahead of Tuesday's motion shows MPs will be asked to note Sir Keir's statements that "full due process" was followed in Lord Mandelson's appointment, that "Sir Olly Robbins was absolutely clear that nobody put pressure on him" to make the appointment and "no pressure whatsoever exists in relation to this case".

The vote will take place on the same day that former senior government figures are due to give evidence to the Foreign Affairs Committee, including the prime minister's former chief of staff Morgan McSweeney and former senior civil servant at the Foreign Office Sir Philip Barton.

Lord Mandelson was sacked seven months after starting the Washington DC job over his friendship with the convicted sex offender Jeffrey Epstein.

Sir Keir apologised for making the appointment but has continued to face questions over whether the vetting process was rushed.

Badenoch said Sir Keir had misled Parliament when he told MPs that "full due process" had been followed in the appointment process.

She also questioned the prime minister's assertion that "no pressure existed whatsoever" on the civil service to approve Lord Mandelson as the UK's ambassador.

Sir Olly Robbins, who was the senior civil servant in the Foreign Office until he was sacked by the PM, told the Foreign Affairs Committee last week that there was "constant pressure".

He added that this did not affect his decision to give Lord Mandelson security clearance to take up the role.

In an apparent effort to clarify his comments in Parliament, Sir Keir told the Sunday Times there are "different types of pressure".

"There's pressure โ€“ 'Can we get this done quickly?' โ€“ which is not an unusual pressure. That is the everyday pressure of government," he said.

Liberal Democrat Cabinet Office spokeswoman Lisa Smart MP said Labour MPs "must put principle before party and vote to refer Keir Starmer to the Privileges Committee".

Reform UK leader Nigel Farage said he believed the prime minister had misled the House of Commons more than once.

"Boris Johnson tried it - didn't get away with it - no reason why Keir Starmer should," he added.

Zack Polanski, leader of the Green Party of England and Wales, said there were "lots of questions about the prime minister's conduct" and that he would support an inquiry, but noted the issue was a "huge distraction from the toxic combination of low wages and high bills".

Speaking to the BBC Radio 4's Today programme, Dame Emily Thornberry said her committee was investigating the appointment and that she did not want the Privileges Committee to be "duplicating the work we're doing".

"It may be that at some stage in the future, some of the questions haven't been answered, and it is decided that they are of sufficient importance that the Privileges Committee should be involved," she said.

"But I don't really see why we're doing it at the moment, apart from, potentially people trying to score points in advance of the local elections."

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