The British government should work with its Dublin counterpart in setting out the circumstances under which a border poll will take place, SDLP leader Colum Eastwood has said.
The Foyle MP was speaking as fresh research revealed that a majority in the north believes the secretary of state should make clear the criteria for holding a vote on Irish unity.
Some 55% of respondents say the basis under which a referendum on the north's constitutional future will take place should be clearly spelled out.
However, 39% of those surveyed oppose laying out the border poll criteria, according to a LucidTalk poll for the Belfast Telegraph.
According to the 1998 Good Friday Agreement, the secretary of state can call a border poll “if at any time it appears likely to him that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland”.
The British government has consistently refused to specify what this might mean in practice, despite repeated calls to set out the criteria.
Former shadow secretary of state Peter Kyle last year pledged to set out the basis for a referendum if Labour were in power but his successor Hilary Benn has yet to make a similar commitment.
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The vast majority of nationalists (88%) believe the circumstances for a referendum should be clearly set out, as do 75% of Alliance/Green voters.
However, just 17% of unionists agree with more than three-quarters of DUP, UUP and TUV voters against the move.
Mr Eastwood told The Irish News that the British government in consultation with the Irish government should "absolutely publish the criteria for a unity referendum".
"It is a democratic imperative, particularly in light of the UK Supreme Court ruling last year preventing a second referendum on Scottish independence without Westminster’s consent," he said.
"That’s why the next Westminster election will be critical - we need as many MPs as possible who will be there to use our influence to push a new administration to publish the criteria for one of the biggest decisions the people of this island will make together."
A majority of respondents also believe that a simple 50% plus one vote is enough to determine the outcome of a border poll, but seven in 10 unionists disagree and support a 'supermajority'.
Asked what criteria should be taken into consideration for a border poll, a quarter of people think it should be nationalist candidates securing a majority of votes in an assembly election, or a majority of MLAs elected being nationalist.
One in five people believes the criteria should be a majority vote in the assembly for a border poll, while 17% say nationalists making up the largest group in Stormont.
Some 15% think the Secretary of State’s decision should be based on opinion polls continually showing 40-50% in favour of Irish unity, while 18% believe the level of support in polls should be continually over 50%.
Lucid Talk surveyed a 3,046 people took between October 27 and 30.
