Lawyer John Wadham is also a leading Liberty campaigner

Mr Shayler is in a Paris prison after a brief court appearance on Sunday.

Neither Mr Wadham nor Mr Shayler's girlfriend have so far been allowed to visit him in prison.

Mr Shayler was arrested in Paris by French police at the request of the UK Government on Saturday.

He left Britain last year after revealing details about the service to a newspaper, and had been living in exile in a French farmhouse.

The UK Government has 40 days to lodge a request for extradition, and the French have a similar period to consider it.

More in the future? David Shayler's current Website

Mr Wadham said negotiations with the UK Government had been going on for six months to ensure that any disclosures made did not damage UK national security.

It was reported that Mr Shayler was preparing to make further revelations on the Internet, but the Home Office would not say if this prompted his arrest.

Mr Wadham said the Attorney General, John Morris, was acting hypocritically in seeking to charge his client.

Attorney General John Morris is accused of hypocrisy

He said the minister had opposed the Official Secrets Act while in opposition, when Mr Wadham remembered Labour saying it was "too draconian".

He said he could not discuss the details of the case but that the information he sought to reveal was in the public interest.

The Act makes it illegal to reveal anything about the workings of the intelligence agencies, even if the disclosures were made in the public interest.

David Hooper: Represented former spy Peter Wright

Mr Wadham also denied that Mr Shayler has no evidence for his claims, and blamed bureaucracy and the failure of different government departments to communicate for the surprise arrest.

David Hooper, the lawyer who represented another former spy - Peter Wright - has joined Mr Wadham in condemning the goverment.

"If Mr Shayler has committed a crime, one would have expected him to be arrested at the outset and not as a bargaining counter."