The Attorney General's office was ordered today 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 17 March 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 7 March, 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 17 March.
Mr Thomas said today that it was an "exceptional, complex and sensitive case" which had raised many issues.
He went on: "My conclusion is that the balance of the competing public interest tests calls for disclosure of the recorded information which led to, or supported, the concluded views which were made public by the Attorney General in his 17 March statement.
"As the Government chose to outline an unequivocal legal position, on such a critical issue at such a critical time, the balance of the public interest calls for disclosure of the recorded information which lay behind those views.
"By this means the public can better understand the background and rationale behind that published statement and the extent to which reliance upon those final conclusions was in fact justified.
"But I have also concluded that the arguments for maintaining the exemptions are sufficiently powerful that the balance of the competing public interests does not require the disclosure of those parts of the requested information which were of a preliminary, provisional or tentative nature or which may reveal legal risks, reservations or possible counter-argument.
"Nor is disclosure needed where it would prejudice the UK's relations with other countries."