Boris Johnson should resign if he is unable to secure a trade agreement with the European Union, a Tory veteran believes.
North Thanet MP Sir Roger Gale, whose constituency includes Leave-voting Herne Bay, says the Prime Minister's position would be "untenable" if the UK leaves without a deal.
Sir Roger Gale has called for Boris Johnson to resign if an agreement is not made with the EU
It comes after the deadline for negotiations between the two sides was extended by Mr Johnson and European Commission President Ursula von der Leyen, after originally being set for Sunday.
Sir Roger said this morning: "If Mr Johnson fails to reach an acceptable trade agreement with the EU the Prime Minister will also have failed the people of the United Kingdom.
"As a lifelong member of the Conservative party, I believe that Mr Johnson's position as Prime Minister would be untenable.
"As an honourable man, he would have to make way for somebody more able to pick up the pieces, to re-unite the whole country and to show the leadership that Great Britain and Northern Ireland deserves."
Despite the 11th-hour extension to negotiations, Mr Johnson warned yesterday that no deal remains the most likely outcome as both sides struggle to iron out a number of contentious issues.
Sir Roger's intervention follows warnings to the Prime Minister from Conservative Eurosceptics, such as Sir Iain Duncan Smith, to not cave into EU demands.
Some MPs have warned he could face a leadership challenge. One unnamed leading Brexiteer told The Times earlier this month: "If he [Mr Johnson] lets us down, I’ll send my letter in, it is as simple as that.”
Thanet county councillor Barry Lewis, (Lab) of Margate, said: "I congratulate Roger Gale for saying what the majority of the country is thinking.
"The Prime Minister has not fulfilled his election promises to deliver his 'oven ready' deal."
Analysis by political editor Paul Francis
The intervention of Sir Roger Gale is not the kind of thing that Boris Johnson needs when he is still grappling with the EU over a deal.
But while it is certainly unwelcome, it is not going to trigger open warfare over Brexit.
What is most interesting is the timing of the veteran Kent MP’s call for Boris Johnson to stand down if he can’t secure a trade deal. He has not waited to see if one can be struck but has gone public with his misgivings just as the negotiations are at a sensitive stage.
Does this reflect a wider disillusionment amongst backbench Conservative MPs at the Prime Minister's performance? It is hard to say at this juncture but the Prime Minister will be acutely aware that whatever the terms of the UK's departure from the EU, he will not satisfy factions within the party on both sides of the argument.
The uncompromising language used by Sir Roger is also surprising, notwithstanding the MP’s reputation for plain speaking.
In calling for Mr Johnson to stand aside if no trade deal can be agreed, Sir Roger has undoubtedly set a few hares running.
The question is whether he speaks for a larger constituency within the parliamentary party. It would be surprising if others were to stick their head above the parapet just now but if there are others who feel the same, they will have been emboldened by the stand taken by Sir Roger.