Theresa May has been warned not to accept a “dodgy” deal from Brussels by the leader of her Democratic Unionist Party allies.
Ahead of a crunch Brussels summit on Wednesday, Arlene Foster told the prime minister not to accept a plan that would “effectively cut Northern Ireland adrift”.
And, in a direct message to Mrs May, she urged her not to follow an example set by Margaret Thatcher in deal negotiations.
It came as leading Tory Eurosceptic Jacob Rees-Mogg warned Mrs May around 40 Conservative MPs were steadfast in their opposition to her overall Brexit strategy.
In a speech at a Leave Means Leave rally in Torquay he accepted there could be problems in the event of a no-deal or “punishment” Brexit, including chaos at the Channel ports.
But he said if the EU acted like a "mafia-style organisation" then Britain would be "all the better for leaving".
"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,” he said.
In an effort to find a way to avoid a hard border between Ireland and Northern Ireland after Brexit reports have suggested the UK could remain tied to Brussels’ rules beyond the end of 2020 to give negotiators more time to finalise a trade deal.
The potential extension of the transition period, which could see the UK stay in the EU single market and customs union, accept continued free movement and make further payments to Brussels, is being considered as intensive negotiations continue ahead of the European Council summit.
Under the current plans, if there is a Brexit deal the transition period will last until the end of 2020, during which the UK will accept Brussels’ rules without having a seat at the table when they are decided.
But the Guardian and Daily Telegraph reported the option of a potential extension was being considered by negotiators in Brussels to allow extra time to drawn up a deal on the future UK-EU relationship – and avoid the need to use a controversial “backstop” arrangement to prevent a hard border between Ireland and Northern Ireland.
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.
What was Arlene Foster's warning to Theresa May?
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.
Stressing that her party – which has threatened to cause a political crisis by voting down Philip Hammond’s Budget if Mrs May gives way to Brussels – was serious, she 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.”
She added: “This backstop arrangement would not be temporary. It would be the permanent annexation of Northern Ireland away from the rest of the United Kingdom and forever leave us subject to rules made in a place where we have no say.”
In a direct message to Mrs May, she urged her not to follow Margaret Thatcher in accepting a deal she later regretted – referring to the former prime minister’s part in the Anglo-Irish agreement.
“She later deeply regretted the choice she had made," she wrote.
"However, we do not want nor need the regrets of another prime minister.
“We want the right choices made. We want her to stand by her principles and instincts rather than accepting a dodgy deal foisted on her by others.”
Brexit Secretary Dominic Raab said that a provision on customs which was not “finite” would fail to deliver the result of the 2016 referendum.
And Downing Street insisted that Mrs May would never agree a Brexit deal with the EU which “traps” the UK permanently in a customs union.