Andrew Bridgen has slammed the Prime Minister's decision to work with Labour leader Jeremy Corbyn to solve the Brexit impasse.
Appearing on the breakfast show, the European Research Group member said it was "unbelievable" that Mrs May would go to someone who was "unfit to govern" the country.
"If the answer is Jeremy Corbyn, what was the question that Theresa May was asking the Cabinet?" he asked talkRADIO's Julia Hartley-Brewer.
"It is absolutely unbelievable that she would go to someone who she has criticised for being unfit and who is unfit to govern our great country, to decide how Brexit is delivered."
Mrs May announced that she would be meeting with the opposition leader to agree a plan on the UK's future relationship with the EU, after failing three times to get support for her deal in the House of Commons.
It is expected that talks between the two will begin today.
Mr Bridgen added: "It is about the survival of the Prime Minister. She needs to take a long look in the mirror and for the good of our country, our democracy and our party - she needs to go."