The Northern Secretary, Dr John Reid, last night welcomed the IRA statement, but senior Ulster Unionists said it did not go far enough.
Dr Reid, who said the British government had no prior knowledge of the statement, welcomed its acknowledgement of the pain the IRA had caused.
"What we all have to do is to give people the confidence that there will be no return to the type of activities that caused that pain and that we are all committed to resolving our difficulties through exclusively democratic and political means.
"This is a peace process which is in transition, which has come a huge distance; but it won't be completed until everyone is confident that the past is behind us and that the type of actions which brought so much pain have been set aside," he added.
But Ulster Unionist MP, Mr Jeffrey Donaldson, branded the statement a "half-hearted apology" which "doesn't go far enough".
He questioned whether the IRA was committed to the peace process. "What we need to know is that there will be no more innocent people who will die at the hands of the IRA either in Northern Ireland or elsewhere. There are a few people who will allow themselves to be deceived by the IRA's words into believing that there is a commitment to the peace process but I judge the IRA as much by their actions as I do by their words.
"They could tell us the war is over, they could complete the decommissioning process that they were supposed to have completed two years after the [Belfast] Agreement, and they could do what Bertie Ahern has demanded of them and that is disband."
Another senior Ulster Unionist, Lord Kilclooney, formerly Mr John Taylor, rejected the statement as "not sufficient". He said his party did not want sympathy from republicans but "an assurance that the war is over".
"Instead, the statement is words, words and more words. It provides for the IRA to continue, as in recent years, with more purchases of illegal arms, more murders, more beatings of innocent Catholics and more international adventures."
The SDLP leader, Mr Mark Durkan, said the statement would "not wash away the grief" of victims.
The Provisionals' campaign had not just involved some mistakes, but was a mistake in itself, he added.
The DUP's deputy leader, Mr Peter Robinson, said that the only IRA action helpful to the people of Northern Ireland would be a cessation of violence.
"Their statement has all the odour of being more to do with the dilemma they are facing with the Prime Minister than any earnestness on their part to recognise the hurt and anger they have caused," he added.
The Lord Mayor of Belfast, Mr Alex Maskey of Sinn Féin,described the apology as "very significant". He rejected suggestions there was a link between the statement and Mr Blair's imminent speech on how to restore unionist confidence in the peace process.
The Alliance Party's deputy leader, Ms Eileen Bell, said the statement was "a positive step towards building greater confidence in the peace process".
The leader of the Progressive Unionist Party, which politically represents the Ulster Volunteer Force, Mr David Ervine, said the statement should not be dismissed out of hand.
"It's been a long time in coming and we should acknowledge the fact that it has arrived and hope that maybe it heralds a new attitude," Mr Ervine said.