The investigation into who leaked parts of January's Hutton Report into the death of weapons expert Dr David Kelly has failed to find the culprit.
The Sun said the report came from someone 'with no vested interest'
Lord Hutton said he "deplored" the Sun printing many of the key points hours ahead of its full publication.
A spokesman said "a full and careful investigation" had been carried out but was "unable to discover the source".
Sun political editor Trevor Kavanagh told the BBC he was surprised the inquiry had not asked to speak to him.
"I wouldn't have told them anything... but you never know I might have fainted and confessed everything," he told BBC News 24.
It would at least have shown that the inquiry was a serious one and was following the proper procedures, he said.
However, he said, it now seemed the leak inquiry was a "long and pointless exercise" designed to "cover their blushes" at the findings being leaked.
The Hutton Inquiry statement said: "Lord Hutton asked the solicitor to the inquiry to conduct an investigation to try to discover the source of the leak."
"The solicitor carried out a full and careful investigation but was unable to discover the source," it added.
The inquiry into the report's leak was also asked to look into whether there were any other steps which could be taken in the future to ensure that confidential reports did not leak before publication.
However the probe concluded there were "no particular weaknesses" in the measures which were taken to guard the confidentiality of the report, although "steps taken to protect sensitive reports before publication will be kept under regular review".
The content of Lord Hutton's report was closely guarded before its publication in January this year.
The key parties - including Downing Street, the BBC and Dr Kelly's family - were not given copies of it until 24 hours before publication.
At the time, the Tories blamed the government for the leak but Downing Street denied it was responsible, as did the BBC and Tony Blair's ex-press chief Alastair Campbell.
Lord Hutton said in January: "I wish to state that I deplore the reporting of some of the conclusions of my report by a newspaper this morning."
Dr Kelly killed himself in July 2003 after being named as the source for BBC reporter Andrew Gilligan's story claiming the government exaggerated its 2002 dossier on Iraqi weapons.
Mr Kavanagh said he had not seen the report, but had been given details from it by an "impartial" source over the telephone. He has consistently said he would not reveal details about the source.
"What I can tell you is the source had nothing to gain financially or politically, no axe to grind, no vested interest," he told BBC Radio 4's Today programme in January.
The statement announcing the failure to find the culprit added that "for security reasons no further information will be disclosed on the steps taken to identify the leak.