Chris Patten: controversial governor of Hong Kong

Ashdown Demands Hong Kong Inquiry

"Matters of this seriousness should not be left to speculation, innuendo and rumour," said Mr Ashdown.

It is the latest twist in allegations that the former Hong Kong governor, Chris Patten, may have leaked confidential material about the handover of the colony to China to the journalist, Jonathan Dimbleby.

In his book, The Last Governor, Mr Dimbleby describes how Mr Patten was furious about not being told of a "gentleman's understanding" between Britain and Beijing over the thorny issue of direct elections in Hong Kong.

Mr Patten has denied passing "intelligence material" to Mr Dimbleby.

Writing to Tony Blair, Mr Ashdown noted that the substance of the claims in Mr Dimbleby's book "seem to indicate collusion or worse with the Chinese authorities and manipulation of the survey of public opinion (towards democracy) of the people of Hong Kong in 1987.

Jonathan Dimbleby: at the heart of the controversy

Jonathan Dimbleby speaking on the Today programme Dur 7'51"

"These allegations, if true, would cast a very serious shadow on the actions of the then government and on the exercise of our duties on behalf of, and in the interests of, the people of Hong Kong," he said.

Mr Dimbleby has also called for an inquiry. On BBC Radio's Today programme, he said he believed there had been "an atmosphere of collusion" between London and Beijing. He said he would love to know more about it, and supported calls for an inquiry into the matter.

But Mr Dimbleby did not answer directly when asked if Mr Patten had leaked secret documents to him.

"I have made it very clear that I had lots of conversations with Chris Patten, lots of conversations with other people, and I had lots of conversations on confidential terms with those people," he said. "And I retain respect for that old principle that you retain confidences. Therefore I don't divulge sources."

A senior Labour backbencher David Winnick said he would be pressing the Government about the affair when Parliament returned from its summer recess in October.

The government has confirmed that the Foreign Office is conducting an internal inquiry into claims, but Downing Street appeared yesterday to play down the seriousness of the investigation, saying police were not involved.

The Tories have accused Labour of deliberately timing the weekend's announcement of a probe into Mr Patten to divert the public's gaze after a week which culminated in the Uxbridge by-election defeat and news of the break-up of the Foreign Secretary Robin Cook's 28-year marriage.