Nationalist politicians have welcomed Mr David Trimble's call for a referendum on Irish unity.
However, the DUP has said demanding it on the same day as next May's Assembly election is a cynical electoral ploy by the Ulster Unionist leader.
Mr Trimble said he had not yet discussed the issue with the British government. Both Downing Street and the Northern Ireland Office said they had no plans for a referendum but would be talking to Mr Trimble. An NIO spokesman said others would have to be consulted.
Mr Trimble called for the Border poll in his keynote address to the a.g.m. of the Ulster Unionist Council, his party's governing body, in Belfast on Saturday.
He said he was confident a referendum would deliver a clear majority in favour of the Union. It would call Sinn Féin's bluff, copper-fasten partition and kill the issue of Irish unity for a generation.
Unionist critics believed the UUP leader was also attempting to increase the turn-out of moderate unionist voters, thus maximising support for his party which could lose ground to the DUP in the Assembly elections.
Sinn Féin chairman Mr Mitchel McLaughlin said: "We welcome what is the opening gambit of a debate on the last great issue affecting the island of Ireland."
The SDLP chairman, Mr Alex Attwood, said his party was "best placed and best informed" to persuade people in the North about their political future in an all-Ireland context. "Others talk the talk. The SDLP alone is capable of the persuasion necessary to bring this about," he said.
Mr Trimble was returned unopposed as UUP leader as was the Rev Martin Smyth as party president and Mr Jack Allen as treasurer. The anti-agreement MP, Mr Jeffrey Donaldson, topped the poll in the election of four party vice-presidents.
Meanwhile, the SDLP leader and Deputy First Minister, Mr Mark Durkan, has described Mr Trimble's criticism of the Republic as "gratuitously offensive" and "unbecoming of a party leader".
Mr McLaughlin accused Mr Trimble of "gratuitously insulting" the Republic and demanded an apology to the Irish people.