Tony Blair has delayed elections to the Stormont assembly because a promise by the IRA that its "war" is over did not go far enough.

The decision to postpone the elections until the autumn was criticised by the Irish premier, Bertie Ahern and all of the main political parties apart from David Trimble's Ulster Unionists.

Speaking in Downing Street, the prime minister said: "Finally, yesterday afternoon, Gerry Adams did respond and said that the IRA leadership, and I quote, 'is determined that there will be no activities which will undermine the peace process and the Good Friday agreement'.

"That's the general assurance. But there was a point-blank refusal to rule out expressly the activities stated in paragraph 13 of the joint declaration."

Tony Blair said that he wanted an answer to one simple question: "Will those activities continue to be authorised or not by the IRA? Yes or no? It is not a desperately complicated situation. But it is one that requires a very clear answer.

"Despite some of the comment, this is not a game of words. The difference is not in the realm of the superficial or the surreal. It goes to the very soul of the Good Friday agreement."