The uncompromising legal language of the draft agreement is likely to provoke a major row, something all parties to the negotiations have been trying to avoid.

British officials negotiating in Brussels were told by their counterparts that there could be a “sunset clause” included in the legally binding text, which is due to be published in around two weeks. Such a legal device would make the text null and void at a future date should an unexpectedly generous free trade deal, or a hitherto unimagined technological solution emerge that could be as effective as the status quo in avoiding the need for border infrastructure.

As it stands, however, the UK is expected by Brussels to sign off on the text which will see Northern Ireland remain under EU law at the end of the 21-month transition period, wherever it is relevant to the north-south economy, and the requirements of the Good Friday agreement.

The move is widely expected to cause ructions within both the Conservative party and between the government and the Democratic Unionist party, whose 10 MPs give Theresa May her working majority in the House of Commons.

The UK will be put under even greater pressure to offer up a vision of the future relationship that will deliver for the entire UK economy, but the inability of that model to ensure frictionless trade is likely to be exposed. A meeting of the cabinet to discuss the Irish border on Wednesday failed to come to any significant conclusions.

“There will be no wriggle room for the UK government,” said Philippe Lambert MEP, the leader of the Greens in the European parliament, who was briefed in Strasbourg earlier this week by the EU’s chief negotiator, Michel Barnier. “We are going to state exactly what we mean by regulatory alignment in the legal text. It will be very clear. This might cause some problems in the UK – but we didn’t create this mess.”

Barnier has repeatedly warned that Brexit, with the red-lines chosen by Theresa May, means barriers to trade in the form of checks at the border.

In Northern Ireland, the UK government’s contradictory position of seeking to leave the customs union and the single market and yet wanting frictionless trade is said to present not only a danger to trade but a risk to peace.

Earlier this week, George Hamilton, chief constable of the Police Service of Northern Ireland, warned that any infrastructure at the border, however light, would become a target for armed groups and pose a danger to his officers. “The terrorists only have to be lucky once and get a result with catastrophic consequences,” he said.

The EU’s proposed text is said to be the logical consequence of the agreement reached between the European commission and the UK government in December, to allow the talks to move on from the issues of citizens rights, the financial settlement and the Irish border.

The UK government had said that “in the absence of agreed solutions, the United Kingdom will maintain full alignment with those rules of the internal market and the customs union which, now or in the future, support North-South cooperation, the all-island economy and the protection of the 1998 [Good Friday] agreement”.

Despite initial protests from the DUP, the unionists were bought off with paragraph 50 of the joint agreement, in which the British government promised to ensure that there would be no barriers to trade between the British mainland and Northern Ireland.

David Davis, the Brexit secretary, has suggested that the whole of the UK could remain in regulatory alignment with the EU. The DUP trumpeted the concession as evidence that Northern Ireland and Great Britain would be leaving the EU on the same terms.

Those commitments to the DUP are regarded by the EU, however, as an internal arrangement for the British government outside the scope of the legal text.

Speaking at the Policy Forum for Ireland conference in Dublin, Michael D’Arcy, Ireland’s minister of state for finance, public expenditure and reform, said of the commitments to the DUP: “It is not a matter for the Irish government.”

John McGrane, the director general of the British Irish Chamber of Commerce, said there was still a delusional sense within some government departments in the UK that it would be “sorted out”. He claimed there was “an underlying sense of entitlement” that Britain could carry on as it was because it was so important.

“Britain has got zero out of the negotiations so far,” he said. “Does it keep getting zero or does is salvage something? Last week I was at a gathering organised by one of the UK government departments, no disrespect, but it was essentially designed to reinforce the notion that it would be alright, and it was really important that people stood up and said no it might not.”

An EU official involved in the negotiations said the situation in Ireland exposed the “infeasibility” of Brexit on the prime minister’s terms. The source added: “These commitments will come to haunt the British.”

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