Allies of Boris Johnson have risked infuriating Conservatives MPs by claiming the party would be “comically ungovernable” under another leader.
Supporters of the prime minister also hit out at Tory MPs who triggered a vote of no confidence in Mr Johnson, accusing them of lacking a plan to replace him.
The prime minister is due to give a speech to Conservative backbenchers shortly as he fights for his political survival.
Mr Johnson will address a meeting of the powerful 1922 committee in Westminster, two hours before MPs start voting on his future.
Former Tory leadership candidate Jeremy Hunt has become the latest MP to say he should go over the partygate scandal.
As the calls mounted today, John Penrose, the prime minister’s anti-corruption champion, resigned and announced he would vote against Mr Johnson, claiming the Tory leader had broke the ministerial code over Partygate.
Many Tory MPs warn the party cannot continue with Mr Johnson as leader, arguing he has lost the trust of the British public following the revelations that a host of parties were held in Downing Street while the rest of the country was under Covid restrictions.
But allies of the prime minister argue he is still the best person to lead and unite the party.
One said: “I fear that what would happen is that the party would become comically ungovernable [without Mr Johnson].”
Another hit out at rebels they said were trying to oust the prime minister without a plan for who would replace him.
“They want to try to knit the parachute on the way down… that just doesn’t work,” they said.
They rejected the idea that the party had been in a similar situation four years ago when MPs held a confidence vote in then-prime minister Theresa May. That had been a very different prospect, they said.
“When Theresa May left everyone knew we would get Boris and that the party and the country loved him. Now there is no plan.”
The confidence vote comes just a day after a dossier setting out Mr Johnson’s failings spread among Tory MPs.
The paper, entitled Party Leadership, warned that the solution to “end this misery” was to remove Mr Johnson, who it described as “no longer an electoral asset”, from office.
The Conservatives faces two big electoral tests later this month, in by-elections in different parts of England.
