Keir Starmer will urgently 'correct the record' on his appointment of Peter Mandelson - after falsely claiming the disgraced peer was given clearance via 'intensive security vetting'.

The Prime Minister is expected to break his silence next week after No10 today confirmed the former ambassador to the US had in fact failed his security checks.

In an astonishing development, the Foreign Office was said to have pushed ahead with appointing Mandelson as the UK's top diplomat in Washington DC against the advice of vetting officials.

A clip from a press conference in East Sussex on February 5 re-emerged this evening - where a flustered Starmer attempted to wrongly pin the blame for Mandelson's appointment on 'independent' security vetting services.

He said: '[It was] an intensive exercise that gave him clearance for the role, and you have to go through that before you take up the post.'

The Prime Minister added: 'Clearly both the due diligence and security vetting need to be looked at again.'

It is now understood Sir Keir will address the 'depth of fury' in Westminster - after parties across the political divide called for his resignation.

The Labour leader will go to the Commons on Monday and give a statement to 'correct the record', Sky News understands.

Sir Keir is expected to defend himself against allegations he knowingly misled the House by admitting errors have been made - but insisting he was unaware Mandelson had failed his security vetting.

Downing Street today insisted neither the Prime Minister nor any other Government minister was unaware until Tuesday evening, at which point Sir Keir immediately ordered a Whitehall probe.

It only emerged that Lord Mandelson had failed security vetting, over his links to paedophile financier Jeffrey Epstein, when The Guardian newspaper published explosive claims on Thursday afternoon - with No10 remaining silent for nearly three hours.

The newspaper reported that security officials initially denied Lord Mandelson clearance, but the PM had already named him as ambassador and the Foreign Office took the rare step of overruling the recommendation.

There were claims at Westminster that Olly Robbins, the architect of Theresa May's Brexit deal who is now the most senior civil servant at the Foreign Office, is being lined up as a fall guy.

The Foreign Office said it is urgently working to comply with Sir Keir's demand to know how Lord Mandelson was cleared to become US ambassador.

The extraordinary revelations have piled more pressure on Sir Keir's position in Downing Street, with the Tories, Reform UK, Liberal Democrats and Green Party all calling on him to resign over his 'lies' about Lord Mandelson's appointment.

Sir Keir has also been accused of misleading Parliament over his previous claims that 'full due process' was followed in the appointment of Lord Mandelson.

Tory leader Kemi Badenoch said: 'The PM appointed Peter Mandelson before the vetting had been completed, vetting Mandelson failed.

'Starmer then said full due process was followed. THAT is misleading Parliament. I'm only holding him to the same standards to which he's held previous PMs - that if they mislead parliament, they should resign.

'In these dangerous times, Britain cannot afford to have a PM who the country doesn't trust. Starmer has betrayed our national security. He should go.'

Reform's Nigel Farage said: 'Now we discover that he has blatantly lied, the Prime Minister should resign.'

Lib Dem leader Ed Davey also called for the PM's resignation. 'Keir Starmer had already made a catastrophic error of judgement,' he said.

'Now it looks as though he has also misled Parliament and lied to the British public. If that is the case, he must go.'

No10 sources said information about Lord Mandelson's vetting was obtained by officials trawling through piles of documents, as the Government scrambles to comply with MPs' demand for the publication of all files related to his appointment.

A Government spokesperson said: 'The security vetting process for Peter Mandelson was sponsored by the FCDO.

'The decision to grant Developed Vetting to Peter Mandelson against the recommendation of UK Security Vetting was taken by officials in the FCDO.

'Neither the PM, nor any Government minister, was aware that Peter Mandelson was granted Developed Vetting against the advice of UK Security Vetting until earlier this week.

'Once the PM was informed he immediately instructed officials to establish the facts about why the Developed Vetting was granted, in order to enact plans to update the House of Commons.

They said the Government is committed to complying with the parliamentary 'humble address' motion to disclose documents relating to Lord Mandelson's appointment 'in full as soon as possible'.

The cross-party Intelligence and Security Committee (ISC) has been given the final say on what is too sensitive for publication.

'Any documentation within the scope of the humble address that requires redaction on the basis of national security or international relations will be provided to the ISC, the spokesperson added.

'This will include documents provided to the FCDO by UK Security Vetting.'

A Foreign Office spokesperson said: 'The PM has initiated a process to establish the facts of the granting of developed vetting and we are working urgently to comply with that process.'

It is understood that recommendations by UK Security Vetting are non-binding on Government departments.