BBC correspondent Valerie Jones reports on the attempt to silence David Shayler

David Shayler had threatened to defy the government by making disclosures abroad or on the Internet about MI5's work.

But its lawyers have written to Mr Shayler's Internet Service Provider in the US warning that reproducing information from him would breach an injunction and render them liable to action for contempt.

UK Government lawyers also objected to the use of a security service logo which may have given the impression that his site was official.

Mr Shayler said in a statement he was "tempted" to accept offers to make further disclosures so he could raise money to support himself.

He said: "If they (the authorities) were really concerned about national security, they would not have put me in the invidious position of having to look at publishing further stories without the input of the authorities to support my life in exile."

Shayler disclosed MI5 details

Mr Shayler came to prominence in August 1997 when he made a number of disclosures in a newspaper about MI5.

Government lawyers obtained injunctions to prevent further disclosures by him and to stop anyone repeating what he told the newspaper.

Mr Shayler is now based in France and negotiating a deal for an amnesty which would let him return to the UK without fear of prosecution over the initial "breach of confidence".

But talks have broken down and Mr Shayler has since told a newspaper he planned to detail his claims about MI5 on his Website.

Idea of censorship 'ridiculous'

Since last year John Wadham, director of the pressure group Liberty, has been talking to government lawyers to reach a deal. He is also Mr Shayler's solicitor.

He said: "The Internet is designed to provide free access to information. The idea of trying to censor this is ridiculous."

Mr Wadham said Labour voted against the Official Secrets Act when the last government introduced it but seemed willing to use it against Mr Shayler.

The act makes it an offence to disclose anything about MI5 activities, no matter how trivial or how much disclosure would be in the public interest.

Mr Wadham urged the Attorney-General, John Morris, to drop the idea of prosecuting Mr Shayler.

But a spokesman for the attorney-general's office said: "The government would take a serious view of any breach of this injunction."