A 50-page dossier is expected to be released today providing former Prime Minister, Boris Johnson's defence against claims he lied to Parliament over the 'partygate' scandal.

Despite 126 fines and dozens of photographs, Mr Johnson has repeatedly denied claims there was a party held at Number 10 during the pandemic and that he and his party did not break any lockdown rules.

The Privileges Committee - chaired by Labour’s Harriet Harman but with a Tory majority - is expected to publish the lengthy submission from Mr Johnson’s barrister Lord Pannick KC today which will attempt to prove he did not 'mislead' MPs with his assurances to the Commons that lockdown rules were followed.

Good Morning Britain Political Correspondent, Louisa James, said: "The word knowingly, is the crucial one here because it goes to the heart of Boris Johnson's defence this week. 

"That is that when he stood up in front of parliament and said there were no partys, no rules were broken, all guidelines were followed, he believed at the time that he was telling the truth. 

"And his team say this bombshell dossier, which we understand is going to be released this afternoon, will prove that because it will contain messages sent to Boris Johnson by his aids shortly before he appeared in the commons briefing him what to say. 

"They say he was simply following advice from those he trusted and we expect him to make those arguments himself when he appears before those MPs in a four-hour grilling on Wednesday."

Mr Johnson is expected to highlight previously undisclosed WhatsApp messages from senior civil servants and members of his No 10 team showing he had relied on their advice when he made his statements to Parliament.

He will also publish messages which show other senior figures in Downing Street believed the gatherings were covered by the “workplace exemption” in the lockdown rules.

Bicester Advertiser: A picture released released in the Committee of Privileges interim report of Boris Johnson at 10 Downing Street during lockdown.A picture released released in the Committee of Privileges interim report of Boris Johnson at 10 Downing Street during lockdown. (Image: PA)

Following the release of the dossier, Mr Johnson will hope to clear his name at a public hearing on Wednesday.

What is the role of the Privileges Committee?

The Privileges Committee is examining evidence around at least four occasions when Mr Johnson may have misled MPs with his assurances to the Commons that lockdown rules were followed.

The committee will publish its findings on whether Mr Johnson committed a contempt of Parliament and make a recommendation on any punishment, but the ultimate decision will fall to the full House of Commons.

If the MPs believe he did mislead the House, they will consider whether it was “reckless or intentional” and amounted to a contempt of Parliament.

A suspension of 10 sitting days or more for Mr Johnson could ultimately trigger a by-election in his Uxbridge and South Ruislip seat.

Ms James, on Good Morning Britain, said: "It will be a huge moment for Boris Johnson because it could decide his political future. 

"It's a big moment for the conservative party who haven't quite decided what to do with him. 

"But it's also a big moment for those who lost loved ones in the pandemic and have long called for Boris Johnson to lose his job."

An estimated £220,000 of taxpayers’ money has been allocated for Mr Johnson’s legal bills and his allies insisted he expected his position to be “vindicated” after submitting a “detailed and compelling” account of his case.

There is "no evidence" I mislead parliament says Boris Johnson

After an interim report by the committee earlier this month said evidence strongly suggested breaches of coronavirus rules would have been “obvious” to the then-prime minister, Mr Johnson claimed it was “clear” that he had not committed a contempt of Parliament.

Bicester Advertiser: Boris Johnson has repeatedly denied claims there was a party held at Number 10 during lockdown.Boris Johnson has repeatedly denied claims there was a party held at Number 10 during lockdown. (Image: PA)

He said there was “no evidence in the report that I knowingly or recklessly misled Parliament” or failed to update it in a timely manner.

Former minister Conor Burns, an ally of Mr Johnson, said: “Boris Johnson’s contention is that what he told the House of Commons was, to the best information supplied to him, true when he told that to Parliament, and I welcome the fact that he is going to bring forward evidence to back up that.

“It’s not unusual, anyone who has appeared as a minister in the House of Commons knows that you rely very heavily on briefing that you’re given.”