Kemi Badenoch is calling on Labour MPs to prioritize national interest over party loyalty by supporting an investigation into claims that Keir Starmer misled Parliament about Peter Mandelson’s appointment as the US ambassador.

On Tuesday evening, MPs are set to vote on a motion demanding a probe into whether Starmer, the Prime Minister, deceived Parliament regarding his controversial decision to nominate Mandelson for the diplomatic role.

A defeat for Starmer in this vote could destabilize his already struggling government and potentially lead to his resignation.

In an effort to avert this crisis, Downing Street initiated a vigorous campaign on Monday to ensure party unity, warning Labour MPs they might face a strict three-line whip to secure their compliance.

However, in an article for the Daily Mail on Tuesday, Badenoch argues that MPs, regardless of party affiliation, have a responsibility to hold Starmer accountable for allegedly showing ‘contempt’ towards Parliament.

She urges Labour backbenchers to remember their duty in the Commons goes beyond merely shielding the Prime Minister from political embarrassment.

‘Labour MPs now face a test of their own,’ the Tory leader said.

‘They can circle the wagons, obey the Whips and tell themselves this is just politics. Or they can remember they are MPs before they are members of the Labour Party.’

Keir Starmer could face an inquiry into whether he lied to Parliament, if it is backed by a Commons vote on Tuesday evening

The sleaze probe would look at whether Starmer knowingly fed Parliament false information when he said Peter Mandelson (left) had passed Foreign Office vetting for the job of Ambassador to the US

Kemi Badenoch is urging Labour MPs to put country before party and back a sleaze probe

Sir Keir faces a day of torment over his handling of the Mandelson scandal. 

He is accused of misleading Parliament by repeatedly claiming that ‘full due process’ was followed at all times, despite the fact that Mandelson was given the job before he was security vetted.

Mrs Badenoch also questioned Sir Keir’s claim to MPs that ‘no pressure whatsoever’ was applied to officials to push through Mandelson’s appointment.

Former Foreign Office chief Sir Philip Barton is expected to confirm he warned against sending Mandelson to Washington when he appears before MPs on Tuesday morning. 

He is also expected to back his successor, Sir Olly Robbins, who said officials were ‘under constant pressure’ from No 10 to sign off the appointment.

In a bombshell intervention last night, former Foreign Office security chief Ian Collard agreed with Sir Olly’s claim that there had been pressure from Downing Street to carry out Mandelson’s vetting quickly.

No 10 is also braced for the PM’s former chief of staff, Morgan McSweeney, to give evidence on the scandal this morning.

Opposition MPs are today seeking an investigation by the Commons Privileges Committee into whether Sir Keir misled Parliament. 

In a rare move, Commons Speaker Sir Lindsay Hoyle granted permission for an emergency debate on the issue, saying it had been backed by ‘numerous MPs from across the House’.

Commons Speaker Sir Lindsay Hoyle granted permission for an emergency debate on whether there should be an inquiry

Former Foreign Office chief Sir Philip Barton (pictured) is appearing before MPs on Tuesdy morning, when he is expected to corroborate Sir Olly Robbins’s account that the Foreign Office was ‘under constant pressure’ from No 10 to sign off Mandelson’s appointment

It is the same process used by Sir Keir to hound Boris Johnson out of Parliament over Partygate, but the PM insisted his own case was ‘completely different’. 

He told Sky News the Government had ‘huge amounts of transparency going on’ – and branded today’s Commons vote a ‘political stunt’.

Addressing the Parliamentary Labour Party last night, he pleaded with his mutinous MPs to back him. ‘Tomorrow is pure politics and we need to stand together against it,’ he said. ‘It’s important to see the bigger picture here. They want to stop this Labour Government. When we stick together and fight together we are so much stronger.’

Sir Keir has struggled to escape the backlash for pressing ahead with Mandelson’s appointment despite being warned in writing that he had a ‘particularly close’ relationship with paedophile Jeffrey Epstein and questionable business links in Russia and China.

The PM has tried to blame officials, sacking Sir Olly this month after discovering that the appointment was pushed through against the advice of UK Security Vetting without his knowledge. However, he has struggled to convince MPs and even members of his Cabinet of his story.

Angela Rayner appeared to throw the PM a lifeline last night, with allies suggesting she will not vote for the inquiry.

Lib Dem MP Lisa Smart said last night: ‘Labour MPs must put principle before party and vote to refer Keir Starmer to the Privileges Committee.’

Deputy Prime Minister David Lammy yesterday became the latest senior figure to confirm that he warned the PM against appointing Mandelson.

‘There were worries at the time,’ he told LBC. ‘And there was a discussion within government.’

MPs are usually given a free vote on matters of whether Parliament has been told the truth.

Tory grandee Sir Desmond Swayne said it would be ‘an abomination’ if Labour MPs were ordered to fall into line to save the PM’s skin over a question of whether he told the truth.

But panicking Labour Whips are expected to warn MPs they risk suspension from the party if they fail to back Sir Keir today.

And No 10 took the unusual step of selectively releasing a letter from the Mandelson files which they believe strengthens the PM’s case that he told the truth.

The letter from former permanent secretary Sir Chris Wormald said an investigation into Mandelson’s appointment had found that ‘appropriate processes were followed’. But Mrs Badenoch said it was ‘irrelevant’ as it was already clear that Sir Chris’s predecessor Simon Case had advised the PM not to announce the appointment until he had been vetted for security – advice that was ignored.

MPs were told that tens of thousands of files relating to Mandelson – which Parliament demanded in February – will not be released until after the local elections.