Former UK Prime Minister Boris Johnson (Reuters)

Tory support for Boris Johnson is dwindling, with party leaders comparing his response to a cross-party parliamentary inquiry into whether he misled MPs about "Partygate" to the lies of former US President Donald Trump.

Several senior Conservative MPs expressed shock after Johnson and his dwindling band of allies questioned the work of the independent Commons privileges committee and accused it of an "outrageous level of bias" after it said on Friday that there was a significant volume of evidence suggesting that the former Prime Minister may have misled parliament.

A senior MP, who is well informed about Partygate, said, in reference to Johnson and his allies, that “they have gone full Trump. It is wicked. Where will this end? They are desperate.” Another grandee said Johnson was “just like Trump, saying black is white, white is black."

On his account, Tory chair of the military select committee Tobias Ellwood said Prime Minister Rishi Sunak had demonstrated real leadership with last week's agreement on the Northern Ireland protocol but cautioned that Johnson might damage the progress.

Ellwood continued, in regard to the ex-PM's behavior, "If we now keep unified and disciplined, we could win the general election, but not if this current diversion turns into a Trumpian drag anchor."

Other senior Tory members suggested that Johnson may have committed contempt of parliament in the last 48 hours alone by insulting, deriding, and undermining the work of a committee set up by the Commons to investigate whether he had told the truth to MPs.

Sir Bob Neill, Tory chair of the all-party justice select committee and a lawyer, said, as quoted by The Observer, “It is wrong for anyone to try to undermine the work of a parliamentary committee.”

Friends of Johnson claim that the appointment of former civil servant Sue Gray, who conducted the inquiry into Downing Street lockdown parties last year, as Johnson's chief of staff by Labour leader Keir Starmer demonstrated that Partygate was a politically motivated plot to depose a Brexit-supporting PM and benefit Labour.

MPs who support Johnson plan to ask urgent questions about Gray's appointment in the Commons on Monday, which one described as a "constitutional scandal that fundamentally destroys the civil service," according to The Observer.

The government advisory committee on business appointments (Acoba) is set to push Gray's start date back by up to two years to address concerns about potential conflicts of interest, stretching it past the next general election.

Nevertheless, as Johnson's supporters accused it of holding a "political show trial," the privileges committee released a statement clearly denying that it had relied on Gray's assessment to make its own interim findings.

It claimed that none of the evidence gathered from witnesses belonged to Gray and that it had all been independently verified and collated.

According to committee sources, lawmakers have not and will not take Gray's testimony. They stated that the evidence includes written testimonies from 23 witnesses, WhatsApp communications, images from the official Downing Street photographer, and other government-provided information. "It is completely incorrect to imply that what there is [is] from Gray," a lawmaker added.

Downing Street refused to comment on whether Rishi Sunak would continue to support the privileges committee. According to sources, it is completely independent of the government, thus commenting on its activity would be wrong.

The committee issued a 24-page report on Friday, claiming that violations of [lockdown] instructions would have been "clear" to Johnson at the time of the gatherings.

Johnson replied to the initial report on Friday by claiming that it "vindicated" him because it found "no evidence" that he lied to parliament.

In his first response to the committee’s findings on Friday, Johnson said, “The committee has produced a report which I believe totally vindicates me because there is no evidence whatsoever that when I stood up in parliament I said anything I did not believe and therefore there is no contempt."

He added that it was “surreal to discover that the committee proposes to rely on evidence culled and orchestrated by Sue Gray, who has just been appointed chief of staff to the leader of the Labour party."