The DUP leader Arlene Foster, whose party is propping up Theresa May’s minority government, has accused the Irish government of exploiting Brexit to attempt to unify Ireland.

Ms Foster, who will address her party’s annual conference tomorrow, told the Today programme: "The Irish government are actually using the negotiations in Europe to put forward their views on what they believe the island of Ireland should look like in the future.”

She added: “We’ve heard from the foreign minister of the Republic of Ireland just yesterday talking about his aspiration for a united Ireland. He is entitled to have that aspiration but he should not be using European Union negotiations to talk about those issues. What he should be talking about are trading relationships.”

On Thursday, the Irish Foreign Minister Simon Coveney said he hoped to see a united Ireland in his political lifetime.

As Theresa May meets Donald Tusk in Brussels, in yet another attempt to move negotations on to trade, Irish Prime Minister Leo Varadkar has again made clear he will prevent talks from advancing before the issue of the Irish border is made clear.

Both Theresa May and the DUP remain committed to removing the UK from the EU’s single market and customs union, an arrangement which would ordinarily require a customs border to be imposed between Northern Ireland and the Irish republic.

Ms Foster also said Ireland’s hard line on the border issue was preventing the talks moving on. “It is wrong that the Irish government will not allow the process to move forward until they have certain things they demand.

"I have always felt it very difficult to have an agreement in relation to the border between Northern Ireland and the Republic, but we haven’t moved to the next stage to talk about trade.”