Abu Hamza al-Masri, the extremist cleric, was forced to stand trial in an atmosphere that was "totally poisoned" against him, the Appeal Court heard today.

The notoriety of the former imam of Finsbury Park Mosque, north London, meant it was "impossible" for him to receive a fair hearing in the courts.

Edward Fitzgerald, QC, for Abu Hamza, said that when his client appeared in the dock at the Old Bailey earlier this year the impression that he was either a terrorist or al-Qaeda recruiter had been "indelibly printed" on the mind of almost every adult in the country.

The Egyptian-born cleric is seeking to quash his 11 convictions for inciting murder and racial hatred and possessing the Encyclopaedia of Afghan Jihad, an item of use to terrorists.

Abu Hamza, 48, who lost both arms and an eye in an explosion in Afghanistan in 1993, elected to remain in Belmarsh prison - where he is serving a seven-year sentence - rather than attend the hearing.

If he loses his appeal the United States Government will resume its attempt to extradite him to face trial on more serious terrorist charges in New York. He would also face legal action to seize a house he is linked to in Greenford, north west London, in order to pay for his defence costs.

Mr Fitzgerald said it had been fundamentally unfair to put the cleric on trial in 2006 for things he had said in a series of speeches and sermons between 1997-2000.

A "massive sea change" had occurred in the world following the September 11 atrocities.

"A unique series of events supervened which prejudiced his chances of a fair trial," said Mr Fitzgerald. "Those events included the 9/11 attacks in the US and the July 2005 bombings in London and the highly publicised decisions of the Home Secretary to strip him of his citizenship and of the US authorities to seek his extradition.

"It further meant that he was subjected to a relentless campaign of adverse media publicity condeming him as a preacher of hate and inciter of violence and to public condemnation by political figures."

Police had seized videos of some of Abu Hamza’s sermons in 1999 but returned them without taking any action against him. Years later he was charged with offences in relation to the same tapes.

Mr Fitzgerald added: "It was oppressive to prosecute him for speeches of which the state were fully aware and in respect of which the police brought no charges."

The authorities also knew of the character of Abu Hamza’s rhetoric because of extensive contact between him and MI5 and Special Branch during the late 1990s. Intelligence agents, who gave him the codenames "Damsonberry" and "910", told him he was "walking a dangerous tightrope" but not breaking the law.

Mr Fitzgerald said: "He was led to believe that the authorities would not prosecute him for any existing offences, that he had not yet crossed the line into illegality and that he was not, therefore, being interviewed as a suspect but as a source of information and assistance to the authorities.

"His continued co-operation was bought at the price of a clear implication that his conduct to date in his speeches did not amount to a crime and would not be proescuted.

"Moreover the state, by staying its hand, gained the clear benefit of being able to use him as a source of information and comment and for liaison with the wider community he represented." To put Abu Hamza on trial in such circumstances was an abuse of the legal process, Mr Fitzgerald said.

The case was "truly exceptional" because Abu Hamza had been continually in the news and no amount of warnings from the trial judge to the jury to ignore what they had heard about him would have been able to remove the prejudice against him.

The appeal, which continues tomorrow, is being heard by the Lord Chief Justice, Lord Phillips of Worth Matravers, sitting with Mr Justice Penry-Davey and Mr Justice Pitchford.

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