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Lord Butler decided that the attorney general was not pressured by the government to declare the war legal.
The panel 'could not comment' on the legality of Lord Goldsmith's advice
Instead, Lord Goldsmith had effectively told the prime minister that there may not have been a case for military action based on defending Britain's interests.
But he had advised Tony Blair that there must be "strong factual grounds" and "hard evidence of non-compliance and non-cooperation" in order to conclude that Iraq had failed to take "the final opportunity" to disarm itself.
On this basis, Lord Goldsmith had advised, the war would be legal because Iraq would have failed to comply with United Nations resolution 1441.
Speaking at the launch of the report, Lord Butler said: "The prime minister, in reaching his view, took account of false statements and omissions in the declarations submitted by Iraq pursuant to resolution 1441."
This included Iraq's failure to comply with and co-operate fully in its implementation.
It was not for the inquiry panel to comment on the legal merits of the attorney general's opinion, Lord Butler added.
The panel also took evidence from former deputy legal adviser, Elizabeth Wilmshurst, who had resigned over the issue of the legality of war.
But her disagreement related to legal arguments and not intelligence, Lord Butler said.