He wrote to Tony Blair, urging him to give government support to an inquiry by the Foreign Affairs Select Committee, but stopped short of seeking an investigation into Tory claims that Chris Patten, the former Hong Kong Governor, was "smeared" by Mr Blair's aides over the affair.
"We are not interested in Tory allegations of news management. It is not our prime concern," said a spokesman for Mr Ashdown.
Mr Patten, holidaying in France, has denied he leaked classified documents about the deal to Jonathan Dimbleby for his book on Mr Patten's term of office as governor. Mr Patten said that if the allegations of a smear campaign against him where true, the Prime Minister's aides would have been acting like "witch-doctors" and not spin-doctors.
The allegations were made by Sir Brian Mawhinney, the Tory spokesman on home affairs.
He accused Peter Mandelson, Minister without Portfolio, and Alastair Campbell, the Prime Minister's press secretary, of "pointing the finger" at Mr Patten's reputation by briefing the press about an inquiry being mounted by MI6.
Mr Ashdown said he did not believe Mr Patten would have provided secret documents.
He also did not think it was "even conceivable" that the story had been a blatant Government news-management attempt, and pointed the finger instead at Mr Patten's enemies in or near the Foreign Office.
"I'm troubled at the way this came out. I think it's extremely unlikely that the Government has had a hand in this in terms of news manipulation.
"I think it's far more likely that it's come from some source hostile to Chris Patten and all that he has done in Hong Kong, either in or close to the Foreign Office," Mr Ashdown said on BBC Radio.
But he said that was the "small change" of the issue: "The big issue is to what extent ... there may or may not have been a conspiracy, written or unwritten, which did not serve either the best interests of the people of Hong Kong or the best traditions of the British foreign service."
The allegations in Mr Dimbleby's book went "to the heart of the integrity of the British administration and the extent to which it served the best interests of the people of Hong Kong at that time".Reuse content