Former attorney general Lord Goldsmith has strongly criticised the refusal of the Government to make public key documents relating to the Iraq war.
Giving evidence to the official inquiry into the conflict, he expressed "frustration" that crucial documents were not being declassified.
"I want to make it clear that I didn't agree with the decision that has apparently been made that certain documents are not to be declassified but I will give the evidence that the inquiry seeks," he said.
Lord Goldsmith admitted that at first he believed it would not be legal for Britain to invade Iraq without a second Security Council resolution.
He told the inquiry: "At one stage my personal view was that taking all these factors into the balance, there wasn't enough there.
"The balance came down in favour of saying, 'no, a second resolution is needed'... I then ultimately reached, when I had to reach a definitive view on this, a different view."
Lord Goldsmith wrote to Downing Street in July 2002 to stress that Tony Blair did not have the authority to agree with US president George Bush that military action could be launched without a further United Nations resolution, the inquiry heard.
This was not "terribly welcome" to Mr Blair, the former attorney general said.
He said he met Mr Straw on November 7 - on the eve of the resolution being passed - to warn him he should not assume it would be "all right on the night" and that it would provide sufficient authorisation.
Justice Secretary Jack Straw later defended his decision to reject the advice of Government legal advisers in the run-up to the war in Iraq. Mr Straw said there was "no ignorance" of the opinions of senior Foreign Office lawyers. Instead there were "different views" on the legality of the invasion, he said.
