Home Office minister Lord Williams: There was no plot

The allegation was made by David Shayler, the ex-MI5 officer under arrest in France pending extradition to the UK to face charges under the Official Secrets Act.

The allegations are published in the Guardian newspaper in the UK, after first appearing in more detail in the New York Times.

An injunction taken out by the UK Government has prevented most of the media from reporting Mr Shayler's allegations.

'No plot'

Gaddafi: Allegedly targeted by MI6

Home Office minister Lord Williams told Radio Four's Today: "The Guardian I'm sure has quite expensive legal advice which it draws on, and it came to its own conclusion."

"The important point is this - is it true or is it not true that there was an official plot to kill Colonel Gaddafi? It is not true."

Earlier this week a Home Office spokeswoman told the press that it was free to report the general claim that MI6 had plotted to kill Gaddafi because it was not true.

But Lord Williams said that it is a matter for the "internal legal advice" of media organisations to decide whether or not to repeat untrue allegations.

He said that "what really matters to the public" was whether an officially-sanctioned plot to kill Gaddafi existed.

"What you thereafter print, I think, really must be a matter for you bearing in mind your public duties and your public responsibilities."

Asked if, now that the government had officially and publicly denied Mr Shayler's claim that MI6 plotted to kill Gaddafi, the UK media would be be forbidden from reporting the allegation while foreign news organisations were free to do so, Lord Williams said: "I wouldn't have thought, in respect of what I specifically have said, there would be a problem."

'Carbomb plan'

David Shayler, who used to work on the Libyan desk of the domestic security service MI5, says that in February 1996 MI6 agents tried to kill Colonel Gaddafi by placing a bomb under his motorcade.

Mr Shayler says the agents targeted the wrong car, killing several bystanders.

He also alleges that the agent running the operation was paid $160,000 for the assassination attempt and had ties to a fundamentalist group in Libya.

In March 1996 Libyan opposition groups said Colonel Gaddafi had escaped an assassination attempt in the Libyan city of Sirte.

They said the Libyan leader survived, but others had been killed. Responsibility for the attack was claimed by a militant Islamic group.

Under UK law MI6 is permitted to carry out acts overseas that would be illegal at home, so long as it has the authorisation of the foreign secretary.

At the time the assassination attempt is alleged to have taken place the foreign secretary was Malcolm Rifkind.

Mr Shayler is currently in a Paris jail after being arrested at the weekend. He has been on the run since he gave accounts of his work for the security service to a British newspaper.

He was also due to publish information about MI5's operations on the Internet.

French police arrested Mr Shayler at the request of the UK Government. It now has until mid-September to lodge a request for extradition.

Mr Shayler's lawyer, John Wadham, director of the civil liberties group Liberty, has vowed to fight the extradition application.