Over half of Tory MPs will now have to vote against him for Johnson to be ousted from office, and rebels have made the case for why this should happen by circulating a briefing document speaking out against their leader.
The document says keeping Johnson will result in the Tories facing a "substantial defeat" in future general elections and warns that 160 seats are at risk while pointing to polls showing Johnson's declining popularity.
It adds that Partygate and the PM's "denial" of it "represent a major breach of trust with the British population", trust which they say Johnson "cannot win back".
It also says Partygate will continue, particularly as Johnson faces another investigation into it and because questions remain about a November 2020 event that "was not fully investigated by Sue Gray".
"The entire purpose of the government now appears to be the sustenance of Boris Johnson as prime minister," it says. "MPs are having to defend the indefensible, not for the sake of the party, but for one man.
"Should Boris Johnson win a vote of no confidence, but only narrowly, his authority within the commons and the parliamentary party would be destroyed."
It concludes: "They only way to end this misery, earn a hearing from the British public, and restore Conservative fortunes to a point where we can win the next general election is to remove Boris Johnson as prime minister."
\u201cTory MPs who want Johnson out have this weekend been circulating a briefing document setting out why. It warns the party is on course to lose the next election & concludes \u201cthe only way to end this misery, earn a hearing from the British public\u2026 is to remove Boris Johnson as PM\u201d\u201d