Former secret agent David Shayler was freed on bail last night after being charged with two offences under the Official Secrets Act.

The former intelligence officer, who hails from Middlesbrough, faces prosecution over claims of incompetence by his former employers, MI5.

But he will not face charges over a string of other allegations, including claims that MI6 were behind a bungled plot to assassinate Libyan leader Colonel Gaddafi and that the security services failed to act on a warning about an IRA bomb in London in 1983.

His solicitor, John Wadham, who is also director of civil rights group Liberty, said the decision not to charge Mr Shayler over his gravest allegations showed the Government wanted to "back off" from legal action.

But some believe it could rob the former intelligence officer of the public interest defence he intends to mount under European human rights laws.

The former secret agent suggested it was simply "an attempt to prevent the jury from hearing the whole story".

Earlier, Mr Shayler was arrested by Special Branch officers at Dover, when he returned from three years "political exile" in France.

He was taken to Charring Cross police station, London, where he gave a statement to police. As he left, Mr Shayler, 34, said: "I decided to return to Britain to face charges under the Official Secrets Act.

"I have done this to clear my name and to allow a jury of 12 of my fellow citizens to judge me."

He will appear at Bow Street Magistrates Court on Thursday.