The Ulster Unionist Party deputy leader, Mr John Taylor, has accused the Irish Government and the SDLP of attempting to introduce new North-South proposals that are contrary to the terms of the Belfast Agreement.
Mr Taylor made his comments ahead of critical meetings at Stormont today on future cross-Border structures involving Government officials and the North's First and Deputy First Ministers, Mr David Trimble and Mr Seamus Mallon.
The Taoiseach, Mr Ahern, according to a Government spokesman, has also expressed his willingness to travel to Stormont this week to try to finalise the North-South element of the Belfast Agreement, which is crucial to Northern nationalists.
Mr Ahern could also meet Mr Trimble in Dublin on Friday where the First Minister will be addressing a European journalists' luncheon. A UUP spokesman said that, contrary to some speculation, Mr Trimble would not be attending the Fianna Fail Ardfheis at the weekend.
Mr Taylor last night signalled the UUP's intention to play "hardball" on North-South bodies. He told a party meeting in Ballymoney, Co Antrim, that the Irish Government and the SDLP were trying to reintroduce a cross-Border "wish list" which unionists had rejected in April.
"Some of the participants are now trying to claw back into the agenda subjects for North-South bodies which were removed from the agreement. The UUP leaves Dublin and the SDLP in no doubt that we intend to implement the agreement as it is - nothing more and nothing less," he said.
Mr Taylor added that the Northern Secretary, Dr Mo Mowlam, "would be better advised to halt the further releases of prisoners until there is real progress on decommissioning".
Mr Trimble said yesterday that unless decommissioning began it may become "politically impossible" to continue the early releases.
"If the government were to say with regard to prisoner releases what the paramilitaries are saying, that we will do nothing for two years, how then would society react?" Mr Trimble asked.
Mr Mitchel McLaughlin, a Sinn Fein Assembly member, accused Mr Trimble of "latching on to one excuse after another rather than fulfil his obligations under the Good Friday agreement," and said, "There is no link between prisoner releases and anything else in the agreement".
Meanwhile, the Conservative Party continued to pressurise the British government to tie releases to the handover of weapons. After the Tory leader, Mr William Hague, said at the weekend that the message to paramilitaries should be "No decommissioning, no exit", the Conservative spokesman on the North, Mr Andrew MacKay, yesterday said the Prime Minister should make clear "that there will be no further early release of terrorist prisoners until there has been substantial and verifiable decommissioning".
Dr Mowlam, responding in Belfast, said the Tory comments were "unhelpful". She hoped they would not mean an end of the bipartisan Tory-Labour policy on Northern Ireland. "It has proved valuable over the years when we were in opposition and now when they are in opposition, so I hope it is not the end because it would be unhelpful."
On the releases, she said she could not "rewrite the Good Friday Agreement" but she would review the agreement if necessary.
Mr Tom French, the Workers' Party leader, said Mr Hague's comments were unhelpful and "smacked more of petty party politicking than offering any structured criticism or advice.
"It is now time for paramilitaries to make a reciprocal gesture in terms of prisoner releases and start decommissioning in some shape or form. However, remarks from William Hague will not help that process. In fact it will only prolong it."
Mr Peter Weir, a UUP Assembly representative and member of the anti-agreement Union First group, called on Mr Tony Blair to enact legislation to exclude Sinn Fein from the executive.
"This will allow democratic politicians to move forward together to solve the day-to-day problems for the people of Northern Ireland. It is the best way forward. Indeed, it is the only way forward," he said.