An independent inquiry into the Iraq war will be held in private, Prime Minister Gordon Brown has told MPs.
The inquiry will examine the British government's decision to join the United States-led invasion of Iraq, and Britain's subsequent role in the occupation.
Opposition parties and many Labour MPs have been calling for the probe since shortly after the invasion in 2003.
The inquiry will start in July and take at least a year. It will not aim to "apportion blame", Mr Brown said.
The Conservative Party said it "should have started earlier" and have public hearings. The Liberal Democrats accused Mr Brown of trying to "cover up the path" that led to war.
The inquiry will cover the period from July 2001 to July 2009 and be chaired by civil servant Sir John Chilcot. It will not be completed until after the general election, drawing an angry response from opposition MPs.
The government had been urged to hold the inquiry in public, but Mr Brown said he must take into account national security, and avoid damaging Britain's military capability. He said it would hear evidence in private so witnesses could be "as candid as possible".
It was designed on a similar basis, Mr Brown said, to the Franks inquiry into the 1982 Falklands War and would aim to identify "lessons learned".