The anti-agreement Ulster Unionist Assembly member, Mr Roy Beggs jnr, has called on the British Prime Minister to exclude Sinn Fein from the power-sharing executive.
Mr Beggs said Mr Blair would be breaking his pre-referendum pledges if he did not take action. "It is clear to the people of Northern Ireland that violence is continuing. Republicans and so-called loyalists continue to administer punishment brutally. I therefore call on the Prime Minister to exclude the men of violence."
The UUP representative expressed concern about the vote due to take place at the Assembly on Monday on the new government departments and North-South bodies.
It is not known how Mr Beggs will vote. A vote by him against the party, which is calling for a Yes vote, would be considered symbolically significant.
An opinion poll in yesterday's Belfast Telegraph showed that half the people in the North believe the UUP should enter a power-sharing executive with Sinn Fein even if the Provisional IRA does not decommission.
A total of 51 per cent said the UUP should take a leap of faith and join Sinn Fein in the executive in the hope that decommissioning would occur. However, 23 per cent said the party should refuse to take its seats and paralyse the process.
Twenty-one per cent said the UUP should take its seats but refuse to co-operate with Sinn Fein in the executive. The "leap of faith" option was more popular with Catholics (85 per cent) than Protestants (29 per cent).
Among UUP voters, 36 per cent said the party should enter the executive but refuse to co-operate with Sinn Fein. Thirty per cent favoured entering and co-operating even without decommissioning, and 33 per cent said the UUP should refuse to take any ministerial posts. Asked if they would vote the same way again in the referendum on the Belfast Agreement, 81 per cent said they would and 12 per cent said they would not.
The results were welcomed by a UUP Assembly member, Mr Michael McGimpsey, who said they showed the majority of people in the North still supported the agreement. Meanwhile, the 32 County Sovereignty Movement has expressed disappointment at Sinn Fein's response to attacks on republicans who oppose the Belfast Agreement.
Ten days ago Mr Paddy Fox, a former Provisional IRA prisoner from Co Tyrone who was critical of the Sinn Fein leadership, was abducted and beaten. He claimed the Provisionals were responsible.
Mr Joe Dillon of the Sovereignty Movement said: "We are disappointed and saddened by the refusal of Sinn Fein to publicly disavow and call for a halt to attacks upon prominent republicans who oppose the Stormont deal."
Mr Dillon said the Belfast Agreement was clearly not working and had nothing to offer republicans. "The promise of peace, prisoner releases and the unification of our country at an undefined date were used to disguise what truly lay at the heart of the Stormont deal, the acceptance of British rule in Ireland, a minority unionist veto and the reinforcement of partition."
The North's Victims Minister, Mr Adam Ingram, yesterday met relatives of those abducted, killed and secretly buried by the Provisional IRA during the Troubles. He promised the British government would "use every available opportunity to maintain the pressure on people in a position of influence" to obtain information about the bodies.