In a stinging attack on Mr Sunak in her resignation letter, Ms Dorries accused Rishi Sunak of abandoning “the fundamental principles of Conservatism" and said “history will not judge you kindly".
She criticised him for “discarding” Boris Jonhson’s policy commitments, and asked: “What exactly is it you do stand for?”
“It is a fact that there is no affection for Keir Starmer out on the doorstep. He does not have the winning X factor qualities of a Thatcher, a Blair, or a Boris Johnson, and sadly, Prime Minister, neither do you,” the former Culture Secretary said.
“Your actions have left some 200 or more of my MP colleagues to face an electoral tsunami and the loss of their livelihoods, because in your impatience to become Prime Minister you put your personal ambition above the stability of the country and our economy.
“Bewildered, we look in vain for the grand political vision for the people of this great country to hold on to, that would make all this disruption and subsequent inertia worthwhile, and we find absolutely nothing."
I have submitted my resignation letter to Prime Minister Rishi Sunak, today.
— Rt Hon Nadine Dorries (@NadineDorries) August 26, 2023
She also accused Mr Sunak of leading attacks on her resulting in “the police having to visit my home and contact me on a number of occasions due to threats to my person”.
She is expected to be appointed by Chancellor Jeremy Hunt to the historical position of Steward and Bailiff of the Three Hundreds of Chiltern on Tuesday, the arcane process which MPs use to resign.
This will enable the writ to be moved when Parliament returns on September 4 for the by-election, which will be held in the coming weeks.
The Tory former minister had angered voters, opposition MPs and some in her own party by remaining in post for ten weeks since pledging in June she would leave her parliamentary seat with “immediate effect” in protest at not getting a peerage in Boris Johnson’s resignation honours list.
She had said she was delaying her exit while she investigates why she was refused a seat in the Lords.
Her claim that Mr Sunak removed her peerage nomination was strongly denied by Downing Street.
Mr Sunak previously said Ms Dorries' voters were not “being properly represented", but did not move to expel her.
In an interview with the The Mail on Sunday, Ms Dorries said it was “nonsense" her constituents have been ignored and that she was “disappointed" the Prime Minister made comments to that effect.
She said she had written a book titled The Plot: The Political Assassination Of Boris Johnson, which led her to conclude she could no longer remain as a backbench MP.
Mid-Bedfordshire was a solidly Conservative seat at the 2019 general election, with the Tories holding a 24,664 vote majority.