Tony Blair has said he “regrets deeply and profoundly the loss of life” in Iraq since the 2003 invasion.
The former prime minister said his apparent refusal to express regret for the decisions that led to war at his first appearance before the committee had been misinterpreted.
His words were met with cries of “too late” from the public gallery.
Mr Blair also repeated his warning about the “looming” threat from Iran during the four hour session.
Earlier, Mr Blair revealed that he had privately assured US President George Bush “you can count on us” eight months before the Iraq war.
The private note will remain secret – despite calls for it to be published by Iraq inquiry chairman Sir John Chilcot.
He also revealed he disregarded Lord Goldsmith’s warning that attacking Iraq would be illegal without further UN backing because it was “provisional”.
The ex-PM said he had believed his top legal officer would change his position on whether a second UN resolution justifying force was needed when he knew the full details of the negotiations.