Lord Hutton “deplored” the breach of elaborate security arrangements designed to prevent such disclosures, adding: “I am considering what investigative and legal action I should take against the newspaper and its source.”

The Conservatives immediately sought to pin the blame on the Government which, together with the BBC and other key players in the inquiry, had given binding undertakings against disclosing material from advance copies of the report distributed on Tuesday.

Liam Fox, the Tory chairman, said: “The Government’s fingerprints are all over the leaking of this document. It is a despicable act from a morally bankrupt government.” Tony Blair demanded a retraction of the allegation.

Alastair Campbell, Downing Street’s former communications director, who is no longer part of the Government but returned to No 10 on Tuesday to read an advance copy of Lord Hutton’s report, denied leaking it. The BBC and David Kelly’s family also said that they were not responsible.

There were persistent rumours yesterday that the newspaper may have obtained the document from a worker at the official Stationery Office printing plant in Bermondsey, southeast London, where the reports were produced.

Senior executives at the newspaper are said to have spent days planning an operation to obtain the report. It may also be significant that The Sun published an exclusive story on Tuesday morning about security arrangements at the printing plant where, it said, workers were searched when they left the building and had to wear special tags restricting their movements.

The Stationery Office said that there was no evidence to suggest that there had been any breach in the pre- approved security processes.

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