Defence Secretary Geoff Hoon has been cleared by Lord Hutton of masterminding an "underhand strategy" to name Dr David Kelly.
Geoff Hoon has been "vindicated" said his former Cabinet colleague Stephen Byers
Mr Hoon would almost certainly have faced calls to resign if the Hutton report had concluded he had acted "duplicitously".
But Lord Hutton wrote: "My conclusion is that there was no dishonourable or underhand or duplicitous strategy by the government covertly to leak Dr Kelly's name to the media."
The judge said the decision by the Ministry of Defence (MoD) to confirm Dr Kelly's name if pressed by journalists was not part of a covert strategy to leak his name.
He said it was based on the view that it was impossible to keep Dr Kelly's identity a secret.
Lord Hutton said another consideration for the MoD was that "it did not think it right that media speculation should focus, wrongly, on other civil servants".
Alastair Campbell's diary suggested it was Mr Hoon who gave the former Downing Street press chief the most support in his bid to use Dr Kelly to undermine the BBC's report and put pressure on the corporation to retract it.
He denied there was any strategy to expose Dr Kelly as part of the government's battle with the BBC, despite Mr Campbell's diary assertion that he and Mr Hoon agreed Mr Gilligan would be sunk if Dr Kelly was the source.
Lord Hutton's report said he was satisfied, from the evidence of Mr Hoon, Mr Blair and several other crucial witnesses that between 4 and 8 July the government was worried it would be charged with a cover-up if it kept secret the fact that a civil servant had come forward to identify himself as Mr Gilligan's source.
Lord Hutton said: "I am further satisfied that this was the principal reason why it was decided to issue the MoD statement on 8 July."
He said the MoD was "at fault and to be criticised" for failing to tell Dr Kelly his identity as the suspected source would be confirmed to journalists who suggested it but Mr Hoon was cleared of direct responsibility.