The Ulster Unionist MP, Mr Jeffrey Donaldson, has warned the British Prime Minister, Mr Tony Blair, against "fudging" the issue of IRA decommissioning to facilitate Sinn Fein's entry to government.
The Lagan Valley MP, who walked out of the multi-party talks on Good Friday last year because he felt the decommissioning provisions in the Belfast Agreement were inadequate, said there should be no further appeasement of the IRA.
"If Tony Blair thinks that the necessity of the decommissioning of IRA weapons can be simply set aside to bring Sinn Fein on board, then he can think again," he said.
"No amount of spin-doctoring, fudging or further appeasement by Tony Blair and his ministers in the Northern Ireland Office will persuade us from our conviction that IRA decommissioning is absolutely essential. Any concocted form of words from Downing Street will not be enough.
"What we need is firm evidence that the IRA has changed and that people like Martin McGuinness are committed to exclusively peaceful and democratic means," Mr Donaldson said.
The Prime Minister was urged by the Democratic Unionist Party's Assembly member for Lagan Valley, Mr Edwin Poots, to form the Northern Ireland executive without Sinn Fein.
"The government has been happy to proceed with implementing the Belfast Agreement in spite of there being a large minority opposed to it. It should therefore not be allowing Sinn Fein, with only 17 per cent of the vote, to hold them to ransom.
"While the Belfast Agreement did not adequately address the issue of decommissioning, democracy demands that it should take place and that no terrorist or terrorist sympathiser can become an executive minister while they are inextricably linked to a fully-armed terrorist organisation."
Another anti-agreement unionist, Mr Peter Weir, who represents North Down in the Assembly, said Mr Blair should be warned that "unionists have had more than enough of clever formulas and ambiguous words".
