Theresa May faced pressure from Brexiteers within her party and her DUP parliamentary allies to take a tough line with Brussels ahead of a crunch summit.
Democratic Unionist Party leader Arlene Foster warned the British Prime Minister not to accept a “dodgy” deal which would “effectively cut Northern Ireland adrift”.
And leading Tory Eurosceptic Jacob Rees-Mogg warned Mrs May that around 40 Conservative MPs were steadfast in their opposition to her overall Brexit strategy.
At a Leave Means Leave rally in Torquay he accused the British Government of adopting an approach of “managing decline” for the UK rather than seizing the opportunity of Brexit.
Mr Rees-Mogg, chairman of the Tory European Research Group, said 39 of his colleagues were more “tough-minded” than him on their opposition to the Government’s entire Brexit strategy set out in the Chequers plan.
“Those 39 will not turn, I will not turn and there are growing numbers beyond that who are determined that we should deliver on the Brexit that we promised,” he said.
The “future of our country is at stake, the future of our party is at stake”, he said as intensive negotiations continued before Wednesday’s European Council summit in Brussels.
“We must make sure that Chequers in binned, that this idea of a customs union, the sheer lunacy of paying £3.5 billion a year to subsidise the European Union for all eternity is binned,” Mr Rees-Mogg said.
“We are close, we are almost there, we just need to be steady for a few more weeks and if we do that the prize is there to be grasped.”
He accepted there could be problems in the event of a no-deal or “punishment” Brexit, including chaos at the Channel ports.
But he added: “If there are queues at Dover, if the M20 becomes a car park, if there are certain difficulties for a short time because the EU decides to cut off its own nose to spite its face, if the EU is a mafia-style organisation that says ‘if you want to leave we will kneecap you’ then all the better for leaving, because you have to get out of that organisation.”
Meanwhile, the issue of the border between Northern Ireland and Ireland continued to pose a headache for Mrs May as it is one of the last remaining obstacles to achieving a divorce deal.
In an effort to find a way to avoid a hard border, reports have suggested the UK could remain tied to Brussels’ rules beyond the end of 2020 to give negotiators more time to finalise an overall trade deal.
The Guardian and Daily Telegraph reported that the option of a potential extension to the transition period was being considered by negotiators in Brussels to allow extra time to draw up a plans for the future UK-EU relationship – and avoid the need to use a controversial “backstop” arrangement to prevent a hard border.
The Department for Exiting the European Union said it would not comment on speculation.
The need to resolve the backstop issue is a political headache for the Prime Minister, who depends on the votes of the 10 DUP MPs to prop up her administration in Westminster.
The European Union’s version, which would see just Northern Ireland remain aligned with Brussels’ rules, has been called unacceptable by Mrs May and is loathed by the DUP.
Mrs May’s counter-proposal, set out in June, was for a “temporary customs arrangement” for the whole UK, but Tory Brexiteers are suspicious this could turn into a permanent situation, restricting the freedom to strike trade deals around the world.
Former foreign secretary Boris Johnson, writing in the News Letter, said: “The only way to put things back on the right track is to ditch the backstop and then to chuck Chequers”.
He warned that the UK faced its “greatest national humiliation since Suez” adding: “We will be heading for colony status, with many laws imposed on us, with no control over our trade, and with internal checks at the behest of a foreign power. ”
And in a strongly-worded article in the Belfast Telegraph, Mrs Foster warned against the EU’s backstop proposal and also stressed that she would not accept any measure that resulted in extra checks for goods travelling between Great Britain and Northern Ireland.
Her party has threatened to cause a political crisis by voting down Philip Hammond’s Budget if Mrs May gives way to Brussels and Mrs Foster said: “The DUP’s actions this week are not as some have suggested about ‘flexing muscle’.
“This is no game.
“Anyone engaging in this in a light-hearted way foolishly fails to grasp the gravity of the decisions we will make in the coming weeks.”
Downing Street insisted that Mrs May would never agree a Brexit deal with the EU which “traps” the UK permanently in a customs union.
The pledge came amid continued speculation over possible ministerial resignations if the British Prime Minister gives too much ground ahead of the Brussels summit next week.
Stewart Jackson, who was chief of staff to former Brexit secretary David Davis, said it was “quite possible” that another Cabinet minister could follow the example of his former boss and resign.
— BBC Newsnight (@BBCNewsnight) October 12, 2018
Stewart Jackson, former Brexit minister David Davis’s special advisor said weekend resignations over Brexit were “quite possible”.