Former Cabinet minister Jacob Rees-Mogg has warned the Conservatives against any attempt to block Boris Johnson if he seeks to stand in another parliamentary constituency.
Mr Rees-Mogg told the Mail on Sunday that to do so could plunge the party "into civil war".
Mr Johnson resigned as the MP for Uxbridge and South Ruislip on Friday over the investigation into Partygate.
Mr Rees-Mogg was knighted in his resignation honours earlier that day.
A Conservative Party spokesman said all potential constituency candidates, former MPs or otherwise, went through the same process.
Meanwhile, Labour leader Sir Keir Starmer said Prime Minister Rishi Sunak had "failed to end" what he called "the Tory chaos", and called for a snap election.
Mr Johnson stepped down as an MP after he saw in advance a report by the Commons Privileges Committee investigating whether he deliberately misled the Commons over lockdown breaches in Downing Street.
In an explosive 1,000-word statement on Friday evening, Mr Johnson said: "I have received a letter from the Privileges Committee making it clear - much to my amazement - that they are determined to use the proceedings against me to drive me out of Parliament."
He argued the draft was "riddled with inaccuracies and reeks of prejudice", calling the committee a "kangaroo court" whose purpose "has been to find me guilty, regardless of the facts".
The committee will not confirm the sanction recommended until it publishes its report into Mr Johnson, likely this week.
But two sources have told that the sanction the committee recommended in the documents sent to Mr Johnson was a suspension from the Commons lasting more than 10 days.
The 10-day period is significant because if the House of Commons approves the suspension of an MP for 10 sitting days or more, that MP then faces a recall petition in their constituency, which can lead to a by-election.
Mr Johnson also suggested Mr Sunak was not running a "proper Conservative" government
In his resignation letter, the former prime minister left open the possibility of a return, saying he was "very sad to be leaving Parliament" before adding - "at least for now".
Hours earlier, one of his biggest allies, former Cabinet minister Nadine Dorries, unexpectedly stepped down from her Mid Bedfordshire seat.
And on Saturday, another supporter Nigel Adams resigned, triggering a third by-election for the Tories.
Speculation about Mr Johnson's future in politics has subsequently included the suggestion he could stand in another seat, although there is no indication this is likely.
Writing in the Mail on Sunday, Mr Rees-Mogg said Mr Johnson could "easily get back into Parliament at the next election" - and he was "in pole position to return as Conservative leader if a vacancy should arise".
But the former business secretary went on: "I would most strongly warn Conservative Party managers against any attempt to block Boris if he seeks the party nomination in another seat.
"Any attempt to do so would shatter our fragile party unity and plunge the Conservatives into civil war."
In contrast, former Conservative deputy prime minister Michael Heseltine has said Mr Johnson should not be allowed to run to be a Tory MP again.
Writing in the Observer, he says: "To me it is inconceivable that in these circumstances he could stand as a Conservative member of parliament again."
Addressing the former PM's resignation letter, Mr Heseltine writes: "Words are designed to make his audience believe whatever they want to believe. There is no anchor to any discernible truth or sense of integrity."
He adds that Mr Johnson will leave Parliament and "have little to do with the reality of the mess he left behind".
Elsewhere in the Sunday Mirror, Mr Starmer accused Mr Sunak of failing to stand up to Mr Johnson and agreeing "to hand gongs to a cast list of cronies".
"Rishi Sunak must finally find a backbone, call an election, and let the public have their say on 13 years of Tory failure," he added.
A government source rejected that and said Mr Sunak was focussed on delivering "what the British people want."