British prime minister Theresa May must put forward proposals for a review of the backstop within a week if she wants a Brexit deal concluded by Christmas, the Government has indicated.

Senior figures in Dublin say Michel Barnier, the European Union’s chief Brexit negotiator, must see firm plans by next week at the latest if a withdrawal agreement is to be reached by the end of the year.

They believe Mrs May sought a phone call with Taoiseach Leo Varadkar yesterday in order to tell her cabinet she had asked for a review of the backstop.

Mrs May is due to update her ministers on the Brexit talks today and is under pressure in the UK to detail how Britain will exit the backstop, which seeks to avoid a hard border in Ireland even if there is no future EU-UK trade deal.

It is understood Mrs May did not specifically raise the prospect of the UK unilaterally withdrawing from the backstop with the Taoiseach, but Mr Varadkar nevertheless made clear his “consistent” position – that such a suggestion is unacceptable.

Irish figures believe Mrs May would have known the Taoiseach’s likely response before making the call.

Review mechanisms

The mechanisms of a review – to which the Taoiseach is open, as long as Britain cannot withdraw from the backstop unilaterally – were not discussed.

“It was more the principle of it,” said a source, who added that the matter was raised more as a “concept” rather than how it would work in practice.

It was added that a firm proposal is needed by “next week, at the latest” in order to conclude a withdrawal agreement by Christmas. It was stressed that a successful outcome was still possible.

“But to be done in an orderly way, any new proposals would need to be tabled next week,” a senior Government source said.

Downing Street dismissed speculation about an imminent breakthrough in the talks. It characterised Mrs May’s call to Mr Varadkar as an opportunity to take stock of the progress being made in the negotiations.

“They agreed that the intention was that the backstop should only be a temporary arrangement and that the best solution to the Northern Ireland border would be found by agreeing a future relationship between the UK and the EU,” a spokesman said. “In order to ensure that the backstop, if ever needed, would be temporary, the prime minister said that there would need to be a mechanism through which the backstop could be brought to an end.”

Brexit secretary Dominic Raab dismissed reports that he was on the verge of resigning, after his suggestion to Tánaiste Simon Coveney that Britain should be able to unilaterally end the backstop within three months of its entry into operation was rejected.

The Irish Times reported yesterday that the final Brexit deal is set to include a backstop that will apply to the entire United Kingdom, but will have additional measures for Northern Ireland to ensure there is no hard border.

A Northern Ireland-specific backstop would effectively give way to one that would apply across the entirety of Britain for customs only.

However, the withdrawal agreement would also contain additional measures – on both customs and regulations – that would apply on the Border.

Sources confirmed yesterday this was the “direction of travel” and added that weeks of intense legal and drafting work lay ahead to make it a reality, if a deal was struck.

Varadkar calls UK ‘a divided kingdom’: page 6