Taoiseach Bertie Ahern's plan to let Northern MPs speak in the Dáil would, if successful, mean the Republic still lays claim to Northern Ireland, the Ulster Unionist Party leader, Sir Reg Empey, has said.
During an hour-long meeting between the two men in Government Buildings in Dublin, Mr Empey sharply criticised Mr Ahern's proposals, which have already been rejected by Fine Gael and the Labour Party.
The Taoiseach has proposed Northern MPs, notably those in Sinn Féin and the SDLP, should be able to address all 166 TDs.
However, he believed that the TDs should meet as a committee of the Dáil, rather than in plenary session, before Northern MPs would be granted access.
Mr Empey said the Taoiseach, speaking in Belfast last week, had made clear "that the constitutional issue was settled. If you create an artificial situation where people from another jurisdiction have a right to appear here, then you are saying that the issue is not settled.
"Is there anything wrong with people invited to attend a committee to give their views? In and of itself, that is not a problem.
"But that is not what is being proposed. What is being proposed is a formalised relationship that is different from anywhere else," Mr Empey said.
The electorate in the Republic voted to remove Articles 2 and 3 of the Constitution, which laid claim to Northern Ireland, as part of the Belfast Agreement.
The Government and Ulster Unionists had agreed measures under the agreement to improve north/south co-operation.
"Let us keep to that. Let us develop and build on that. Let us not complicate things and bring in measures that collide with that," he told journalists after his meeting.
The SDLP has warmly welcomed Mr Ahern's move, and Sinn Féin has made Northern representation in the Dáil one of its key demands.
