British Prime Minister Gordon Brown has announced an independent inquiry into the Iraq war but said evidence would be heard in private.
Mr Brown told the House of Commons that the inquiry would look at the run-up to the war in 2003, the war itself and the following 'reconstruction' period.
To jeers from Conservative Party MPs, he said it will take a year to report, which will take it beyond the next general election.
The Labour government has consistently said an inquiry will be held after the UK's combat role in Iraq has ended.
British troops conducted their last combat mission on 30 April and their withdrawal is expected to be completed by 31 July.
Mr Brown said that with the last British combat troops about to return home, now was the right time to 'learn the lessons' of the 'complex and often controversial events' of the last six years.
He said he was establishing an independent privy counsellor committee of inquiry to look at the period from summer 2001 to the end of July this year.
'The inquiry is essential so that by learning lessons we will strengthen the health of our democracy, our diplomacy and our military.
'The inquiry will be fully independent of Government. The scope of the inquiry is unprecedented.
'It covers an eight-year period, including the run-up to the conflict, the full period of conflict and reconstruction.
'The committee of inquiry will have access to the fullest range of information, including secret information.'
Opposition leaders attacked the decision to hold the inquiry behind closed doors and the nature of the panel conducting the investigation.
Conservative Party leader David Cameron said he was 'far from convinced the Prime Minister has got it right'.
He said: 'The whole point of having an inquiry is that it has got to be able to make clear recommendations, go wherever the evidence needs, to establish the full truth and to make sure the right lessons are learned.
'And it has got to do so in a way which builds public confidence.'
Liberal Democrat leader Nick Clegg said: 'A secret inquiry conducted by a clutch of grandees hand-picked by the Prime Minister is not what Britain needs.'
