Andrew Lewer, the Northampton South MP has revealed he is one of the Conservatives who have submitted letters calling for the Prime Minister to step down.
In a strongly worded statement, he said that Sunday's confirmation of the UK-EU withdrawal deal had allowed him to make up his mind.
He said: "Now that the withdrawal deal has been passed by the EU Council and the scale of the appalling mismanagement of the negotiations has become apparent, led by the Prime Minister, I can confirm that I have now submitted a letter to the Chairman of the 1922 committee calling for the Prime Minister to step down as leader of the Conservative Party and for a leadership election to take place.
"This has not been an easy decision for me to make, but it is the right one."
And Mr Lewer also stated that he will vote against Mrs May's Brexit withdrawal deal when it comes before Parliament next month.
Despite Northamptonians voting for Brexit in 2016, he believes her deal goes against his party's 2017 general election manifesto, which said the UK would leave the single market and customs union.
Calling the agreement a "non-Brexit", Mr Lewer set out his reasons why he intends to vote against the Government.
He said: "The deal brought to us by the Prime Minister is poor - much worse than Chequers in fact. Given that I had already declared in public that I would not support Chequers, my decision about whether to support the Meaningful Vote on this 'Chequers Minus' deal is relatively clear.
"I stood on a Conservative manifesto which promised that, if elected, a Conservative government would take the United Kingdom out of the Customs Union, out of the Single Market and the jurisdiction of the European Court of Justice (ECJ).
"This 'deal' achieves none of those things and divides Northern Ireland from the rest of the UK in a totally unacceptable way and in contravention of my most deeply held principles.
Mr Lewer continued: "It is worse than staying in the EU; at least we then had MEPs, a Commissioner and a seat at the European Court of Justice and thus some influence as a Member State.
"The 'deal' means we achieve none of the potential freedoms of Brexit but take all the EU's rules and restrictions without a seat at the table."
Both Wellingborough MP Peter Bone and Kettering MP Philip Hollobone have already publicly stated they have sent letters calling for Theresa May to resign.