Nadine Dorries has provoked fury after she demanded her Tory colleagues to stop investigating whether Boris Johnson lied over Partygate.
The Culture Secretary led attacks on the Commons Privileges Committee slamming the all-important investigation as a "witch hunt".
If Mr Johnson is found to have lied to Parliament over Partygate, he could face a suspension from the Commons for 10 or more sitting days and a recall petition, which, if signed by 10% of his constituents, would trigger a by-election.
Ms Dorries said the investigation represented the "most egregious abuse of power".
Environment minister Lord Goldsmith said the committee was "clearly rigged" against Mr Johnson, despite having a Tory majority.
Tory MP Lia Nici, an ally of Mr Johnson said: "Political enemies of Boris Johnson are so scared of him they are trying everything to get him out of politics.
"So undemocratic."
It follows reports that a number of the committee members - including some of the Conservatives - have made public comments critical of Mr Johnson's conduct over Partygate.
The Prime Minister's official spokesman said No 10 stood ready to assist the committee in its inquiries - and could continue to do so after Mr Johnson leaves office next month.
"There is a process for this. We will respond to the Privileges Committee in their work in due course. We want to look at this properly and abide by the process," the spokesman said.
"This is something Parliament voted for. We will assist the committee in their inquiries so they can bring it to a conclusion.
"We would expect the committee to abide by the rules in that circumstance."
The Downing Street parties, in breach of Covid rules, were among the scandals that forced Mr Johnson's resignation as Tory leader.
The MPs on the committee intend to call Mr Johnson to give oral evidence in public in the autumn, under oath.
The Prime Minister's spokesman meanwhile has defended Mr Johnson's holiday with his wife, Carrie, in Slovenia amid criticism he was "missing in action" during the cost-of-living crisis.
"I think the public understand that it is not unusual for the Prime Minister - for ministers - to take some time off during the summer recess," the spokesman said.
The spokesman said the trip had not involved the use of taxpayers' money, but declined to say whether Mr Johnson - who is now back working in Downing Street - had paid for it himself.
"No taxpayers' money was used for this. This was a private holiday. Any declarations will be made if required," the spokesman said
Tory MP Angela Richardson tweeted: "Given that some colleagues sharing the Daily Mail article have been subject to death threats themselves, I scratch my head in wonder at the lack of empathy."
Laura Farris swiftly noted that she had stepped down from the Privileges Committee last month.
But insists she has "full confidence" in its members and the mandate given to it.
