Jacob Rees-Mogg has fired off a warning to mutinous Tories that an election could be needed if Boris Johnson was ousted from Government.
The Commons Leader claimed a new Tory leader would need to go to the polls to get a fresh mandate from the public as Mr Johnson's future hangs in the balance.
There is no rule forcing a new Prime Minister to send voters to the ballot box if they have taken over between elections.
Gordon Brown succeeded Tony Blair as PM in 2007 but didn't go to the polls until 2010, while Mr Johnson himself took over from Theresa May in July 2019 but he didn't hold election until December that year.
But Mr Rees-Mogg's comments will be perceived as a warning shot to angry Conservative MPs who are waiting for Sue Gray to publish her 'partygate' report before they move against the PM.
Allies of the PM have made increasingly bizarre attempts to support him, with one saying he had been "ambushed by cake" at a surprise birthday celebration - and another saying he hadn't "robbed a bank".
Mr Rees-Mogg told BBC Newsnight: "It is my view that we have moved, for better or worse, to essentially a presidential system and that therefore the mandate is personal rather than entirely party, and that any prime minister would be very well advised to seek a fresh mandate."
But Foreign Secretary Liz Truss dismissed Mr Rees-Mogg's suggestion that an election would be needed if there was a new Tory leader.
Ms Truss told the BBC : "That is complete hypothetical speculation. I believe the Prime Minister should continue in office. I think he's doing a great job.
"He's apologised, he's admitted that mistakes were made."
Asked if she supported the PM "come what may", she said: "Absolutely."
Justice Committee chairman Bob Neill branded Mr Rees-Mogg's comments "legal nonsense".
He tweeted: "Whatever one’s views on the PM, it has to be said that this proposition is constitutional and legal nonsense, and, ironically, wholly inconsistent with the doctrine of the supremacy of Parliament."
The Prime Minister's future is on a knife-edge as top civil servant Sue Gray prepares to publish her highly-anticipated report into the Downing Street party saga.
Officials have reportedly handed over photos of parties in Downing Street, including pictures of the PM and people close together with wine bottles, according to Sky News.
Ms Gray's report will be given to No 10 before it is published, with Mr Johnson expected to come to Parliament to make a statement on the findings.
The timescale was thrown into doubt after Metropolitan Police Commissioner Cressida Dick stunned the Government by announcing a police inquiry into "a number of events" alleged to have taken place in No 10 and Whitehall during the pandemic.
Mr Johnson could become the first PM to be interviewed under police caution if detectives find elements of criminal wrongdoing.
He will face Keir Starmer for a tense Prime Minister's Questions clash as Westminster braces for Sue Gray's findings.
Ms Truss said the report was expected "imminently" but it had not gone to Downing Street on Wednesday morning.
Northern Ireland minister Conor Burns, a long-time ally of Mr Johnson, defended the PM's presence at a surprise birthday bash in the Cabinet room on June 19 2020.
No 10 accepted Mr Johnson briefly attended the surprise do, when indoor social events were banned, where Carrie Johnson allegedly led guests in a rendition of "Happy Birthday" and presented the PM with a cake.
Mr Burns told Channel 4 News he had been "ambushed by cake" and it was "not a premeditated, organised party".
Meanwhile, Tory backbencher Andrew Rosindell claimed the PM had not done anything very serious.
"He's made mistakes, no question about that, we all do," he concedes.
"I think we've all done it, let's not be so judgemental that the Prime Minister of the United Kingdom has not committed some horrendous, terrible crime the deserves the entire Government to be derailed."
He claimed lots of people "break the law in small ways", adding: "You know, he's not robbed a bank."
