Boris Johnson has been accused of trying to "intimidate" the parliamentary investigation into his conduct days before he is due to step down from office.

Downing Street yesterday published legal advice requested by the Government regarding the Privileges Committee investigation into whether Mr Johnson lied to Parliament.

Lord Pannick, a leading barrister, claimed the committee is adopting an “unfair procedure” and “fundamentally flawed” approach and it would be deemed as “unlawful” in a court.

Although Mr Johnson is due to leave office next week, investigation is going ahead with its inquiry into whether he committed a contempt of Parliament by telling the House on several occasions that there were no lockdown-busting parties in Downing Street.

LONDON, ENGLAND - NOVEMBER 06: Prime Minister Boris Johnson leaves 10 Downing Street for Buckingham Palace on November 6, 2019 in London, England. The British Prime Minister is visiting Queen Elizabeth II at Buckingham Palace to officially mark the dissolution of Parliament ahead of a December 12th General Election. This will be the first winter election held in the U.K. for nearly a century, with the 1923 election producing a hung parliament. (Photo by Stefan Rousseau - WPA Pool /Getty Images)

It came as removal vans were spotted leaving Downing Street as the Tory leadership contest drew to a close when the voting closed at 5pm.

Lord Pannick, argues in the 22-page document that “the committee has failed to understand that to prove contempt against Mr Johnson, it is necessary to establish that he intended to mislead the House”.

“In our opinion, the committee is proposing to adopt an approach to the substantive issues which is wrong in principle in important respects, and the committee is also proposing to adopt an unfair procedure,” his legal advice states.

“But for Parliamentary privilege, a court hearing a judicial review application brought by Mr Johnson would declare the committee’s report to be unlawful.”

He also suggested that a failure by the committee to make an explicit distinction on whether Mr Johnson misled MPs intentionally could have a “chilling effect” on parliamentary debate, with MPs fearful of mis-speaking.

A spokesperson for the Privileges Committee previously denied there had been a change to the rules or to terms of reference after allies of Mr Johnson claimed it used to only matter whether the House had been misled deliberately.

Labour MP Chris Bryant, who chairs the Privileges Committee but has recused himself from the partygate inquiry, dismissed the Government-commissioned legal opinion by Lord Pannick as “disgraceful bullying”.

“Lord Pannick’s bizarre ‘opinion’ has no formal status and is wrong on several counts,” he wrote in a series of tweets.

“You would have thought that Boris Johnson would want to clear his name in front of the Privileges Committee instead of trying to intimidate it.

“It’s time this disgraceful bullying stopped. Let’s hear and see the evidence. If Johnson has a good case to make, he’ll be vindicated. If not, he should take his punishment.”

If he is found to have lied to Parliament, Mr Johnson could be suspended from the Commons or even kicked out in a by-election after a recall petition.

Boris Johnson’s successor will be announced on Monday, taking over as prime minister the following day.

Polling last night showed that only 12 per cent of the public think Liz Truss will be a good prime minister, with voters split on whether she will be better or worse than Mr Johnson

The research by YouGov, ahead of her presumed victory in the contest over Rishi Sunak, suggested that over half of the country think she will be poor or terrible at the job.

Boris Johnson accused of trying to 'intimidate' investigation into lying to Parliament