THERESA May has been put on notice by Brecon and Radnorshire Conservative MP Chris Davies.
The "life-long" Eurosceptic MP has said he has "not yet" joined other MPs from the Brexit backing European Research Group (ERG) in submitting a letter of no confidence in the PM, who has been rocked by two resignations from her cabinet, after she presented her plan, negotiated with the European Union, for Britain’s withdrawal from the body.
Mr Davies said he doesn’t believe at present enough Tory MPs would vote against the PM to trigger a leadership challenge.
The cabinet, by a majority rather than unanimously, backed the plan after Mrs May presented it to them last night but before she even presented it to MPs in the Commons this morning the man who negotiated on her behalf, Brexit secretary, Dominic Raab quit the cabinet and he was soon followed by work and pensions secretary, Esther McVey.
Further pressure has been heaped on Mrs May by prominent backbencher and chair of the ERG group Jacob Rees-Mogg who has said he will submit a letter of no-confidence in the PM.
Brecon and Radnorshire MP Mr Davies said: "I am a committed lifelong Euro-sceptic and always have been. However even if the majority of the country does share this view unfortunately the majority of the House of Commons does not and we do have to very careful how we proceed at this sensitive juncture.
"I am a member of ERG Group in Parliament and I am sure you may have read about other members submitting letters of no confidence in the Prime Minister. I have not done so as of yet."
Under the Conservative Party rules Mrs May would face a leadership challenge if 48 of her MPs send letters of no-confidence. She would need the backing of 158 MPs to see off a challenge and her position would then be safe for a further 12 months.
Mr Davies said: "If enough letters are sent in this triggers a vote of no confidence where more than half the MPs have to vote against the Prime Minister. At present I do not believe there are enough MP’s to reach that number. If the Prime Minister survives such a vote, another vote cannot happen for another 12 months."
The MP, who was first elected in 2015 and increased his majority at the 2017 snap election, said he will study the 580 page agreement in detail over the coming days.
He said a failure to get the deal through Parliament could potentially lead to a second referendum or Labour leader Jeremy Corbyn becoming the Prime Minister.
He said: "Until I have read through the document in detail and looked at what genuine alternatives we have I will not be rushed into a decision.
"Whilst I agree that a bad deal is worse than a no deal, we need to look at what happens next if this deal does not go through Parliament. Many MP’s are concerned that if this does not have sufficient support it could potentially lead to a second referendum, Jeremy Corbyn in power and attempts to keep us in the EU.
"A second vote would be profoundly undemocratic and I would be totally against any attempt to rerun the referendum campaign."
The MP added: "Over the next few days I will studying the 580 page plan in detail and will be talking to colleagues as to the best way we can ensure the British public get the Brexit they voted for whilst also keeping Jeremy Corbyn out of Downing Street.
"Whilst this may not be the response that you are looking for I hope you will understand my reasoning behind holding off, and trust that any decision I make will be in the interest of the 17 million people that voted to leave as well as those who voted to remain."
Labour has repeatedly called for the government to stand aside and allow it to negotiate Brexit.