Theresa May is facing mounting pressure to secure a breakthrough in EU negotiations after the Democratic Unionist party expressed shock at the handling of the Irish border question and Brexit-supporting Conservatives said the time had come to walk away.

Senior cabinet members also voiced unease at May’s tactics, and complained they were not informed in advance about Downing Street’s plan to promise the EU some form of “regulatory alignment” to help move the divorce talks on to the next stage.

Sources warned that key Brexit supporters in May’s top team would object if they believed that anything was agreed that could limit the UK’s ability to diverge from the EU in the future.

Quick Guide Why is the Irish border a stumbling block for Brexit? Show Counties and customs Inside the EU, both Ireland and Northern Ireland are part of the single market and customs union so share the same regulations and standards, allowing a soft or invisible border between the two.

Britain’s exit from the EU – taking Northern Ireland with it – risks a return to a hard or policed border. The only way to avoid this post-Brexit is for regulations on both sides to remain more or less the same in key areas including food, animal welfare, medicines and product safety. The 'backstop' in Theresa May's Withdrawal Agreement was intended to address this - stating that if no future trade agreement could be reached between the EU and the UK, then rules and regulations would stay as they are. This has been rejected by Brexit supporters as a 'trap' to keep the UK in the EU's customs union, which would prevent the UK striking its own independent trade deals. There are an estimated 72m road vehicle crossings a year between Northern Ireland and the Republic of Ireland, and about 14% of those crossings are consignments of goods, some of which may cross the border several times before they reach a consumer. Brexit supporters say this can be managed by doing checks on goods away from the border, but critics say it will be difficult to police this without any physical infrastructure like border posts or cameras, which could raise tensions in the divided communities of Ireland.

Interactive: A typical hour in the life of the Irish border Photograph: Design Pics Inc/Design Pics RF

On the day after May was forced to step back from securing a deal on divorce negotiations after a last-minute intervention from the DUP:

Party leader, Arlene Foster, revealed that she had been asking the government for the wording of text relating to the Irish border for five weeks. She said it was a “big shock” when the document landed on Monday morning because “we realised there was no way we could sign up to that text”.

Former Tory leader Iain Duncan Smith said it would be “intolerable” to bind the UK to EU regulations prior to trade talks, telling the BBC that the government was starting to “stare at the edge of what is a price that we simply cannot afford to pay”.

Former cabinet minister Nicky Morgan hit back, saying: “Walking away when the Brexiteers encounter difficulties they never bothered to anticipate is not in the national interest, betrays the futures of millions of young people and those who never wanted to leave in the first place.”

May was due to talk to Foster and Sinn Féin leader Michelle O’Neill on Tuesday night but the DUP leader delayed her conversation with the prime minister, amid suggestions that the unionist party believed there was too much work still to be done on the wording of the divorce deal text.

Senior cabinet sources revealed that discussions of May’s recent inner-cabinet on Brexit talks had covered the question of how to calculate the divorce bill and questions relating to the European court of justice but not regulation and the Irish border.



And it was even suggested that David Davis only saw that the word “alignment”, which caused much of the controversy, was added to the text on Sunday evening. A Whitehall source insisted that simply reflected “how late the text was being worked on”.

The Brexit secretary was called to address MPs about the issue on Tuesday in an urgent question from Labour’s Keir Starmer. He tried to reassure the DUP, on whom the Tories rely for votes, by promising that any Brexit deal that applies to Northern Ireland would also cover the rest of UK.

Davis admitted that the government was seeking regulatory alignment with the EU in some circumstances, but insisted that it would be UK-wide and that it did not mean retaining exactly the same rules as the EU.

“The presumption of the discussion was that everything we talked about applied to the whole United Kingdom,” he said. “Alignment isn’t harmonisation. It isn’t having exactly the same rules. It is sometimes having mutually recognised rules, mutually recognised inspection – that is what we are aiming at.”

The phone call with Foster, which Downing Street said was due to go ahead, had not been agreed with the DUP and the party was reluctant to go ahead without an agreement on the text. The Guardian understands that there remained fundamental disagreements about the wording on Tuesday, with “radical surgery” required to make progress.



Sources revealed that the Irish government had requested that the text include a section on what might happen if there is no trade agreement between the EU and UK, and so the Irish border becomes difficult to solve.



In those circumstances, which Downing Street sources said they believed would not happen, May was willing to offer some alignment. But the DUP fear that would separate Northern Ireland from the rest of the UK.

Q&A What is regulatory alignment? Show Inside the EU, both Ireland and Northern Ireland (as part of the UK) are part of the single market and customs union so share the same regulations and standards. The only way to avoid a hardening of the border after Brexit is to ensure regulations and standards on both sides remain more or less the same in areas like food, medicines and so on. This might imply a permanent acceptance of EU rules – something that would be anathema to hardline UK Brexiters and the DUP, who reject anything that would "decouple" the North from the UK. David Davis told parliament that regulatory alignment would not mean adopting exactly the same rules as the EU but "mutually recognised" rules and inspections. However, an official in Brussels countered that regulatory alignment would mean that the UK would have to implement rules from Brussels without having any influence over them. What is the government’s plan for ‘regulatory alignment’?

Davis says the UK could continue to follow some rules of the EU’s single market. This would help avoid a hard border, but would also limit the UK’s ability to diverge from EU regulations. What does the EU think?

Davis thinks the UK and EU can agree to meet the same aims, while achieving them in different ways. The EU believes this could see its standards on workers’ rights and the environment undercut. Can it even work?

Parliament cannot bind its successors. This principle would mean a deal would never be completely secure for more than five years – putting its feasibility in doubt. Photograph: PA

Davis tried to reassure the unionists that would not happen after facing a string of interventions from Scottish, Welsh and English MPs who insisted that any deal must be UK-wide.

But Foster said her party’s reading of the words suggested they were “making a red line down the Irish Sea”.

DUP MP Nigel Dodds focused his ire on the Irish government in a passionate intervention during the debate in parliament. He said the republic had advanced its interests in an “aggressive and anti-unionist way”, and had “set back Anglo-Irish relations and damaged the relationships built up within Northern Ireland in terms of the devolution settlement, and that is going to take a long time to repair”.

He added: “We will not allow any settlement to be agreed which causes a divergence, politically or economically, of Northern Ireland from the rest of the UK, because to do so would not just be politically damaging but would be economically catastrophic for everyone in Northern Ireland – unionist, nationalist, Brexiter or remainer.”

Writing for the Guardian, Starmer suggested that rethinking the red line on leaving the customs union could help solve the problem of committing to a soft Irish border.

He wrote: “The most effective way forward would be for Theresa May to rethink her reckless red lines and to put options such as a UK customs union with the EU back on the table. If she does not, the farcical scenes of Monday will merely be a precursor to the rest of the negotiations.”

Davis claimed that his only red line was delivering the best Brexit for Britain after Jacob Rees-Mogg suggested that regulatory divergence was a must after Brexit.

Meanwhile, May was warned that she has less than a week to salvage a Brexit deal that would open trade talks before the end of the year, amid increasing signs of impatience within the EU over her handling of the process.

EU negotiators expect the prime minister to return to Brussels very soon, but have said time is running out to strike a deal at a European summit next week.



“The show is now in London,” said the chief spokesman of the European commission president, Jean-Claude Juncker. “We stand ready here in the commission to resume talks with the United Kingdom at any moment in time when we get the sign that London is ready.”