The organisation, which recently arranged for the Israeli to speak to Amnesty International UK members via live telephone link at its National Conference in Lancaster, reiterates its call on Israel to allow Mr Vanunu to leave the country if he wishes, and to exercise his rights to freedom of movement, association and expression in Israel.

Israel claims that the restrictions imposed on Mordechai Vanunu's freedom are intended to prevent him from divulging further secrets about Israel's nuclear arsenal.

Vanunu has repeatedly stated that he revealed all the information available to him in 1986.

Amnesty International is concerned that Mordechai Vanunu is being subject to arbitrary restrictions in violation of his fundamental rights.

Despite having served his full prison sentence, the authorities appear intent on continuing to punish Mordechai Vanunu using as a pretext, speculation about what harm his future actions may pose to state security. Amnesty International said:

"Israel is bound by international law not to impose arbitrary restrictions on Mordechai Vanunu, including on his right to travel within the country or abroad, his right to peaceful association with others and his right to express his opinions."

Article 12 of the International Covenant on Civil and Political Rights, which Israel has ratified and is obliged to uphold, stipulates that:

"everyone lawfully within the territory of a State shall, within that territory, have the right to liberty of movement and freedom to choose his residence" and that "everyone shall be free to leave any country, including his own."

On 12 April 2005, Mordechai Vanunu was put on trial for violating the restrictions imposed on him following his release from prison.

He has been indicted on 21 counts of violating these restrictions by speaking to foreign journalists and attempting to leave Jerusalem to attend Christmas mass in Bethlehem.

If convicted, Mordechai Vanunu could face up to three years' imprisonment. The next hearing is scheduled for 19 May.

If Mordechai Vanunu were to be imprisoned for breaching the restrictions imposed on him, Amnesty International would consider him to be a prisoner of conscience.

Background Mordechai Vanunu, who worked as a technician at Israel's Dimona nuclear facility from 1976 to 1985, exposed details of Israel’s nuclear capabilities in an interview with the UK-based Sunday Times in 1986.

Following the revelations, Mordechai Vanunu was abducted in Rome by agents of Mossad, Israel's secret services and secretly taken to Israel.

After a secret trial, he was sentenced to 18 years on charges of treason and espionage.

Mr Vanunu maintained that he acted out of conscience, in order to alert the public about the dangers of Israel's production and possession of nuclear weapons. Mordechai Vanunu was released on 21 April 2004, after having served his full 18-year prison sentence, the first 11 and half years of which were spent in solitary confinement.

Upon his release the Israeli authorities imposed stringent restrictions on his fundamental rights, including prohibiting him from leaving the country, restricting his movements within Israel and prohibiting him to be in contact with foreigners, including journalists.

The restriction orders were to expire after one year but have now been renewed for another year.