BBC Legal Affairs Correspondent Joshua Rozenberg reports from the prison holding Mr Shayler

Mr Shayler spoke after meeting his lawyer, John Wadham, for the first time since his arrest at the request of the UK Government on Saturday.

It was "astonishing" that the government was trying to prosecute him, he said in a statement read by Mr Wadham outside La Sante prison in Paris.

Mr Shayler is willing to stay in prison "to prove any revelations that were made were in the public interest".

John Wadham waited six days to see his client

Mr Wadham, also director of the civil rights group Liberty, had to wait six days to meet his client. He has pledged to fight plans to extradite Mr Shayler to Britain to face charges under the Official Secrets Act.

The statement said: "The matters that I have brought to the attention of the public are vital issues for our democracy.

"I should be protected not prosecuted.

"It is clear that MI6 is acting outside government control. MI5 and MI6 should not be allowed to hide behind secrecy legislation."

Gaddafi plot 'inconceivable'

Mr Shayler called on the government to stop "suppressing whistleblowers" and set up an "independent mechanism to investigate these disclosures".

Since his arrest he has disclosed details of a plot by MI6 to murder the Libya's leader Colonel Gaddafi in The New York Times.

UK Government officials have already rejected as the story as "inconceivable".

But Mr Shayler said: "If agents were paid for an assassination attempt that resulted in the murder of innocent people, those who paid them are the real criminals."

His arrest followed news that he was about to reveal details about the secret service on his Internet site.

He had been living in a remote farmhouse in France with girlfriend Annie Machon since revelations were published last year, trying to negotiate a return to Britain.

Brother criticises delay

Mr Shayler's brother Jeremy criticised the delays in getting to see him.

He said: "He has not seen any family or friends since he was arrested on Saturday and it was more than 72 hours before he was able to see a French lawyer.

"I get the impression they are being very heavy handed with him. We have had no contact with him at all."

Mr Shayler's statement came amid news that the former MI6 agent Richard Tomlinson, who was also questioned by police in Paris but released, has been targeted by British and New Zealand police.

Police in Auckland carried out a search of a room where he was staying.

Mr Tomlinson was served with an injunction on Wednesday to prevent him revealing "damaging disclosures" about his four-year career with the intelligence service.