Sinn Féin has been accused of "opportunistic nationalism" after formally calling for a Border poll immediately after Scottish First Minister Nicola Sturgeon demanded a second referendum on Scottish independence.
Sinn Féin's Stormont leader Michelle O'Neill made no direct connection to Mrs Sturgeon's announcement. Instead she put it down to a UK government that "refused to listen" to the majority in Northern Ireland who voted to remain in the EU.
Mrs Sturgeon said she hoped the next referendum would take place between the autumn of next year and the spring of 2019.
In Belfast, flanked by newly elected Sinn Féin MLAs, Mrs O'Neill said the need for an "Irish Unity Referendum" was urgent and her party wanted to see it take place "as soon as possible".
But, speaking in the Great Hall in Parliament Buildings, she also indicated a Border poll is not a pre-requisite before Sinn Féin will agree to go back into government.
"The British Tories are on the verge of triggering Article 50 to take the North out of the EU against the wishes of the people. This will significantly undermine the Good Friday Agreement and lead to the imposition of a hard Border," she said. "The British government is refusing to listen to the majority of people and parties in the North."
Foreign Affairs Minister Charlie Flanagan said calls for an Irish Border poll were "premature". DUP deputy leader Nigel Dodds said Mrs O'Neill's call was "another prime example of opportunistic nationalism".