They fear that the latest blue-on-blue sniping unleashed by the Conservative former culture secretary’s exit could further damage the party’s prospects at a likely general election next year, amid already dire polling.
Ms Dorries accused Rishi Sunak of heading up a “zombie Parliament” and betraying Tory principles as she formally announced her resignation 11 weeks after she vowed to go.
Continuing her broadside on Sunday, the staunch ally of former premier Boris Johnson said it was “very, very unlikely” the Conservatives will win the next election as she refused to say whether the party will get her vote.
He told the Daily Express: “None of us are blameless in all this, Rishi, Boris, Nadine. All of us got us into this mess.
“The question is how do we get out of it. Rishi’s five pledges are a start but we need to deliver, especially on the economy and fast.
“We need to end the infighting or Keir Starmer wins.”
Senior backbencher Sir Bill Cash told the newspaper: “I think we should be fighting Labour.”
Ms Dorries is expected to leave her parliamentary seat on Tuesday after notifying the Chancellor of her intention to do so on Saturday.
She had come under mounting pressure – including from fellow Tory MPs – to act on her June 9 pledge to step down with “immediate effect” in protest at not getting a peerage in Boris Johnson’s resignation honours list.
Jeremy Hunt is expected to facilitate her exit from the House of Commons under the archaic process of appointing her to be Steward and Bailiff of the Three Hundreds of Chiltern on the first working day after the bank holiday.
This will enable a motion called a “writ” to be moved when Parliament returns on September 4, giving between 21 and 27 working days for a by-election to be held in her Mid Bedfordshire seat.
The electoral test threatens to cause misery for the Prime Minister as Labour and the Liberal Democrats are vying to overturn Ms Dorries’ 25,000 majority in the traditionally safe Tory constituency.
The Conservatives will be fearing a repeat of massive defeats in two by-elections before the summer recess, when Labour overturned their 20,000 majority in Selby and Ainsty and the Liberal Democrats flipped a 19,000 blue majority in Somerton and Frome.
Mr Sunak’s party did manage to hang on to Mr Johnson’s old Uxbridge and South Ruislip seat, but with a much-reduced majority.
The challenge for the Conservatives to defend the seat could be compounded by the divisive circumstances of Ms Dorries’ exit, which she delayed saying she was investigating why she was refused a seat in the Lords.