Unionist politicians are demanding clear statements from the RUC Chief Constable and the Northern Secretary on the IRA's involvement in the murder of Belfast man Mr Charles Bennett (22).
The calls follow confirmation from security and republican sources in yesterday's Irish Times that the Provisional IRA was responsible for the murder of Mr Bennett. He was found shot in the head on waste ground in west Belfast on Friday. He had been abducted. His eyes were blindfolded and his hands bound.
The Ulster Unionist Party MP, Mr Jeffrey Donaldson, said the RUC Chief Constable, Sir Ronnie Flanagan, needed to make clear who he believed was responsible for the murder.
He said the Northern Secretary, Dr Mo Mowlam, should impose sanctions on the republican movement for a "blatant breach of the IRA ceasefire". The sanctions should include a halt to the release of IRA prisoners.
"The IRA must learn that if they engage in violence, there is a price to pay. If there's no price to pay, if the prisoners continue to be released, if the Secretary of State turns a blind eye, if the Chief Constable remains silent, then I and others will conclude that the government lacks the will to deal with these important matters."
The Democratic Unionist Party's deputy leader, Mr Peter Robinson, said the British government should immediately exclude Sinn Fein from the peace process.
"Unless the government realises that it has lost the confidence of the community and acts immediately by excluding Sinn Fein, then decent people are going to lose all faith in what is supposed to be a democratic process."
A Northern Ireland Office spokesman said the RUC was investigating the murder and it was too early to say who was responsible. Dr Mowlam received regular advice from security advisers.
"Everything must be looked at in the round. The fact that there is a small minority dedicated to destroying the opportunity we have for peace is despicable. They are flying in the face of the majority of people in Northern Ireland and Ireland as a whole, as was shown in last year's referendum," he added.
The senior Sinn Fein negotiator, Mr Gerry Kelly, accused Mr Donaldson of trying to bring down the Belfast Agreement. He said he believed the IRA ceasefire remained intact and that Mr Donaldson should be spending his time trying to make the agreement work.
"Jeffrey Donaldson has used every opportunity to undermine the peace process. He is the clear leader inside the UUP of the rejectionists and the wreckers.
"Mr Donaldson's track record is clear. He is not genuinely interested in the victims of conflict. He is not interested in resolving the conflict. He wants peace only on his terms and these are not acceptable to nationalists and republicans."
The DUP Assembly member, Mr Ian Paisley jnr, said the British government should face the reality that the IRA ceasefire was a "sick joke" and exclude Sinn Fein from the Assembly.
"The government must now take on the IRA and their political apologists instead of pandering to them."
The Alliance Party president, Dr Phillip McGarry, said the Belfast Agreement was in "deep trouble". If parties and governments which signed it continued to be ambivalent about the use of violence, then the agreement was "doomed to fail".
He said the British government should clarify its position on "the use of murder as a weapon by the IRA", adding that its failure to take "a principled stand against violence is deeply disturbing".
A man and a woman were being questioned by RUC detectives last night in connection with Mr Bennett's murder. The woman was arrested yesterday and another man who had been held for questioning was released without charge.