An early draft of the government's infamous dossier on Iraq's weapons of mass destruction must be made public, the Information Tribunal says.
David Kelly's death prompted the Hutton Inquiry.
The document, by Foreign Office press chief John Williams, was an unpublished draft of the dossier which was unveiled by Tony Blair on 24 September 2002.
The Foreign Office had appealed against the Information Commissioner's order that it should release the draft.
It is not yet clear whether the Foreign Office will appeal to the High Court.
Weapons expert Dr David Kelly was found dead shortly after being named as the source of a BBC report suggesting the government's dossier on Iraq's weapons of mass destruction was "sexed up".
Balance of disclosure
Dr Kelly cited the example of the claim that Saddam Hussein had weapons of mass destruction which could be used within 45 minutes of him giving an order.
The report led to a high profile dispute between the BBC and Downing Street which culminated in Dr Kelly's death.
The task of investigating the "circumstances surrounding the death" of Dr Kelly was then handed to Lord Hutton who, following a two month inquiry, concluded the scientist had taken his own life.
Lord Hutton criticised the BBC and said the 45 minute claim had not been inserted into the dossier by Downing Street against the wishes of intelligence chiefs, stressing that the head of the Joint Intelligence Committee John Scarlett had had "ownership" of the dossier.
The Freedom of Information request for Mr Williams' draft to be made public was made by researcher Christopher Ames.
A passing reference was made to the Williams draft during the Hutton inquiry, but it was never published.
The Foreign Office (FCO) refused to hand over the document, saying that its publication would "inhibit the free and frank provision of advice and the free and frank exchange of views for the purposes of deliberation".
Mr Ames complained to the Information Commissioner, who concluded that the balance "was in favour of disclosure".
He said there was "a strong public interest in disclosure in order better to inform the public as the process followed in preparing the dossier".
The FCO's appeal against that decision was rejected by the Information Tribunal, which said: "We do not accept that we should, in effect, treat the Hutton Report as the final word on the subject...
"Information has been placed before us, which was not before Lord Hutton, which may lead to questions as to whether the Williams' draft in fact played a greater part in influencing the drafting of the dossier than has previously been supposed."
The tribunal also revealed that the draft was "annotated in two different persons' handwriting, suggesting that at least one person other than the author had reviewed and commented on it".
However, the tribunal has ordered that one of the handwritten notes should be taken off the draft when it is released.
The ruling was welcomed by the Conservatives and the Liberal Democrats, who said it strengthened the case for an independent inquiry into the war.
Shadow foreign secretary William Hague said: "The British public has a right to know what lay behind the decision to take the country to war, just as it has a right to expect a full Privy Council inquiry into the origins and conduct of the war."