The prime minister has faced MPs for the first time since being told to take it easy following his weekend heart scare.

Following a tough day in Northern Ireland, Tony Blair said "two very important things had happened" in the province during the course of the stalled negotiations.

The prime minister said he would examine ways to show unionists that "a substantial act of decommissioning" had indeed taken place.

"I believe that on the basis of what we know that people would be satisfied if they knew the full details," said Blair.

He conceded, however, that the negotiations - which are now on hold - had been "deeply frustrating" for all concerned.

But he remained upbeat about the future of the process. "There were two very important things that happened yesterday," the prime minister told MPs.

"The first was a clear statement by Gerry Adams, that was then endorsed by the IRA, that the implementation of the Good Friday agreement means the end of the conflict in Northern Ireland.

"Secondly his statement...that there should be a cessation of all paramilitary activity."

Iain Duncan Smith, who said he was "clearly pleased" to see Blair back "to full health", called for further commitments from republican terrorists.

The Conservative leader expressed concern that Sinn Fein and the IRA had "not done enough to demonstrate their commitment to exclusively democratic and peaceful means".

Blair's appearance at the despatch box formed part of a concerted effort by Number 10 to show that the prime minister is back to "business as usual".

He had been ordered by doctors to "take it easy" on Monday following his visit to hospital on Sunday.

Downing Street insisted that the prime minister was back to "full throttle" after being admitted to hospital suffering from an irregular heartbeat on Sunday.