The Attorney General's office was ordered yesterday to disclose information leading to his advice on the legality of invading Iraq in 2003.

Information Commissioner Richard Thomas upheld requests for an explanation of Lord Goldsmith's statement to Parliament on March 17 in that year.

In a letter to the Legal Secretariat to the Law Officers, Mr Thomas said the Attorney General's confidential advice to the Government, on March 7, had been "significantly more equivocal in nature".

He added: "There is a public interest in establishing the extent to which published statements are consistent with fuller advice that had been given."

The Attorney's General's office was served with an enforcement notice upholding complaints under the Freedom of Information Act.

The notice required publication of a disclosure statement containing "the substance of information" which led to Lord Goldsmith's written answer to the House of Lords on March 17.

A joint disclosure statement by the Cabinet Office and the Legal Secretariat to the Law Officers said that "events moved quickly" between March 7 and March 17, 2003. Lord Goldsmith's original advice to the Prime Minister had stated that "the safest course" would be to secure a further UN resolution on the use of force, adding that this analysis "may, however, be affected by the course of events over the next week or so".

In the following days, the Chief of the Defence Staff requested a "clear indication of the legal position" while the Treasury Solicitor, as head of the Government Legal Service, asked Lord Goldsmith for a "clear statement as to the lawfulness of military action".

The statement continued: "The Attorney General recognised therefore that he needed to indicate his clear view as to whether military action would be lawful and that the Government would need to set out its position publicly."

On March 13, Lord Goldsmith told his Legal Secretary that, "after further reflection, having particular regard to the negotiating history of resolution 1441 and his discussions with Sir Jeremy Greenstock (the UK's ambassador to the UN at the time) and the representatives of the US administration, he had reached the clear conclusion that the better view was that there was a lawful basis for the use of force without a second resolution".