THE Ulster Unionist leader, Mr David Trimble, has demanded that Sinn Fein be politically isolated if it fails to condemn the London bombing.
The party, he said, must make "a convincing commitment to peaceful means". Without such a commitment, it would return to the "pariah status it had before the ceasefire".
Mr Trimble said Mr Gerry Adams had to be asked if the bombing was the start of a full scale resumption of violence and if he condemned it.
If he refused to do so, Sinn Fein should be excluded from the political process, Mr Trimble said.
He also urged SDLP leader Mr John Hume to break off contact with Sinn Fein until it condemned the IRA.
The Ulster Unionist security spokesman, Mr Ken Maginnis, said he was deeply disappointed by the end of the ceasefire. "I spent 18 months hoping against hope that I was wrong when I predicted this ceasefire was nothing", he said.
Ulster Unionist councillor Mr Chris McGimpsey said it was time for constitutional nationalism to stand up to militant republicanism.
DUP leader the Rev Ian Paisley said the bombing showed that the British government had been fooled by the IRA. "A terrorist is a terrorist until he gives up terrorist weapons and none of them will give up their weapons," he said.
The independent unionist MP for North Down, Mr Robert McCartney, said the British government must now base its policies on the strength of the union and not the "kindness of strangers in Dublin or Washington.
The Alliance leader, Dr John Alderdice, challenged Sinn Fein to condemn the bombing. "If they condemn this outrage and dissociate themselves from those who planted the bomb they can remain within the democratic fold", he said.