The Brexit Secretary will today tell the Conservative conference in Birmingham that “our willingness to compromise is not without limits”, and warns that “we will be left with no choice but to leave without a deal” if the EU’s position threatens the integrity of the Union.

Yesterday the Foreign Secretary, Jeremy Hunt, also struck a defiant tone towards Brussels, claiming the UK will not be the only “prisoner” wanting to leave the EU if it is turned into a jail.

Mr Hunt warned EU negotiators to “never ever mistake British politeness for British weakness” and likened their desire to “punish” the UK to the Soviet Union.

Brexit Secretary Dominic Raab, has insisted that the Government is ready to take Britain out of the EU without a deal if necessary, warning Brussels: 'Our willingness to compromise is not without limits.' Picture: Peter Nicholls/PA Wire

The tough talk comes after the first day of the Tory conference in Birmingham descended into fresh infighting over Brexit, with senior Conservatives hitting back at Boris Johnson for calling the Prime Minister’s strategy “deranged”. The former foreign secretary crashed through the first day of the Tory conference in Birmingham, saying the Chequers plan was “entirely preposterous” and suggesting that Theresa May wasn’t committed to delivering Brexit.

It brought a sharp response from Brexiteers and Remainers, with the former Brexit secretary David Davis mocking Mr Johnson’s plans for a bridge linking Britain and Ireland, and Scottish Tory leader Ruth Davidson calling for a “period of silence”.

In an interview with the Sunday Times, Mr Johnson said: “Unlike the Prime Minister, I fought for this, I believe in it, I think it’s the right thing for our country and I think that what is happening now is, alas, not what people were promised in 2016.”

Last night at a pro-Brexit fringe meeting, Scottish Tory MP Ross Thomson called Chequers an “unmitigated disaster that has humiliated us at home and in the EU, and is breaking this party apart”. The divisions will continue today with a fringe meeting attended by two former ministers calling for a second EU referendum on the terms of the UK’s Brexit deal.

Mrs May insisted she was acting in “the national interest” by pushing ahead with a plan to keep the UK aligned with the EU in trade of goods, in a bid to maintain the status quo along the Irish border and limit the damage to the economy.

The Prime Minister told the BBC’s Andrew Marr programme: “I do believe in Brexit. Crucially, I believe in delivering Brexit in a way that respects the vote and delivers on the vote of the British people while also protecting our union, protecting jobs and ensuring we make a success of Brexit for the future.”

She said the onus was on the EU to come forward with detailed explanations of its concerns, along with counter-proposals for discussion. “Chequers at the moment is the only plan on the table that delivers on the Brexit vote and also delivers for the people of Northern Ireland,” the Prime Minister told Marr.

“Where they have problems, let’s actually hear them and it’s only then that you can actually identify what the issue really is, where there are issues that lie behind this.

“My mood is to listen to what the EU have to say about their concerns and to sit down and talk them through with them.”

Ms Davidson questioned why the former foreign secretary was against a plan for the Irish border that was signed off by the full cabinet in December.

“There’s been time over the last two years for debate,” she told the BBC’s Sunday Politics Scotland programme.

“The former foreign secretary was in one of the great offices of state during the time that much of this plan was being constructed – and praised it as soon ago as last year.

“In terms of a period of silence, I would be very welcoming of one.”

Addressing the conference today, Ms Davidson will appeal for unity and call for party members to “go back to our Conservative principles” and reject Brexit dogma.

“We can agree a Brexit deal under the Conservatives, or we can risk handing the keys of Downing Street to Jeremy Corbyn,” Ms Davidson will say. “I know which one I believe is in the national interest. I stand by the Prime Minister.”

In his speech in Birmingham, Mr Raab will describe his approach to Brexit as “pragmatic, not dogmatic”.

“Our proposals would deliver a historic agreement that provides a roadmap out of the EU and a final deal that will be good for the whole country.

“But our willingness to compromise is not without limits. We are leaving the European Union in fact, not just in name. If we can’t obtain a deal that secures that objective… if an attempt is made to lock us in via the back door of the EEA and customs union… or if the only offer from the EU threatens the integrity of our Union. Then we will be left with no choice but to leave without a deal.”

Former Brexit secretary Mr Davis, who quit Mrs May’s Cabinet along with Mr Johnson in protest at the Chequers plan, was dismissive of a series of policy suggestions from the pretender to the Tory leadership. “I think one of the blights of British politics is politicians having fantastic ideas that cost a fortune and don’t do much good,” Mr Davis told Sky News’s Sophy Ridge On Sunday.

“Quite a lot of his ideas, I think, are good headlines but not necessarily good policies.”

Mr Davis confirmed he would vote against Chequers if it came before the House of Commons in its current form, but rejected Labour suggestions that defeat for Mrs May at the hands of Tory rebels would collapse the Government.

“I will vote against Chequers, full stop, and it won’t lead to a general election,” he said.

“We are capable of managing this through.”

Tories ready to walk away from Brexit deal over EU demands