In her resignation letter, the Tory MP accused Rishi Sunak of "demeaning his office by opening the gates to whip up a public frenzy" against her.

The letter to the PM said: "It has been the greatest honour and privilege of my life to have served the good people of Mid Bedfordshire as their MP for 18 years and I count myself blessed to have worked in Westminster for almost a quarter of a century.

"Despite what some in the media and you yourself have implied, my team of caseworkers and I have continued to work for my constituents faithfully and diligently to this day."

The letter went on to say Mr Sunak had abandoned "the fundamental principles of Conservatism" and "history will not judge you kindly".

Ms Dorries, a key ally of Boris Johnson, said she was resigning with "immediate effect" on 9 June. But having not formally vacated her seat, a by-election has not been able to take place.

She said she was delaying her exit while she investigated why she was refused a seat in the House of Lords.

Meanwhile many of her local Conservatives, constituents and fellow MPs called for her to go.