Jamil el-Banna was detained by the US in 2002 after Britain sent the CIA false information about him. He had also failed to accept an MI5 offer to turn informant.

If refused entry to Britain, Mr Banna could be returned to face torture in his native Jordan, from where he fled to Britain in 1994 after alleging ill treatment.

Speaking through his lawyer from Guantánamo, Mr Banna described how he longed to be reunited with his wife and five children, and denied involvement in terrorism. "They should admit the truth - that they have been holding an innocent man for four-and-a-half years. I just want to be home with my family," he said.

Mr Banna's lawyers will launch an emergency court battle within days to seek a guarantee from the government that he will be allowed to return to the UK and be reunited with his family. Today they will mark his 45th birthday but friends and lawyers fear he faces a "nightmare choice" between languishing in Guantánamo or facing torture in Jordan.

Jordan fear

The Blair government, despite its criticism of Guantánamo, has refused to help Mr Banna during his incarceration. At least two other former British resident inmates who were cleared for release have been barred from returning to the UK.

Mr Banna's MP, Liberal Democrat Sarah Teather, said ministers should let him return home to north-west London: "It would be a moral outrage if this government now stood idly by and let him be sent to a country where they know his safety would be at risk."

Mr Banna was granted refugee status by Britain after it was accepted he had been tortured in Jordan.

In 2002 he was seized by the CIA after MI5 wrongly told the Americans that his travelling companion was carrying bomb parts on a business trip to Gambia.

He was taken to Bagram airbase in Afghanistan and then to Guantánamo. He alleges ill treatment in both places and has never been charged with any offence.

This month Mr Banna was seen in Guantánamo by his lawyer, Zachary Katznelson from the group Reprieve. According to Mr Katznelson's transcript of the meeting, seen by the Guardian, Mr Banna said: "The British government has let me stay here for four and a half years. What crime did I commit? Together with the Americans, they have kept me from my children. They have deprived me of the chance to see them grow up, to hold them, to kiss them, to laugh with them, to play with them. There is no way to turn back time, to give me back those moments."

During the visit, Mr Banna was allowed to watch a home video of his children, including his first sighting of his four-year-old daughter Maryam. He said: "If there is any justice and fairness in Britain, the British government should tell the Americans immediately: 'You made a mistake; it is time to get him [Jamil] out of there.' Just tell me you are sorry, that you made a mistake. If they apologised, I would forgive them."

Mr Banna came to the attention of MI5 because he knew Abu Qatada, the cleric accused of being al-Qaida's spiritual leader in Europe. Days before the trip to Gambia an MI5 agent went to Mr Banna's home in an attempt to recruit him. He is also wanted in Spain, which has expressed an interest in extraditing him.

His friend, Bisher al-Rawi, was also seized by the US on the trip to Gambia and imprisoned in Guantánamo for four years. He was released in March after it emerged he had helped MI5 monitor Abu Qatada.

Speaking from Guantánamo, while shackled to the floor, Mr Banna said: "I have always told the truth. I have no information about terrorism. I've said since the very first day: put me on trial anywhere at any time. I will gladly stand up and tell my story. And I know that a fair court would set me free. But there is no chance of that here in Guantánamo. There is no justice here." Mr Banna said his diabetes is not being treated and his sight is deteriorating.

Mr Katznelson said: "Now he's been cleared for release, he faces the start of a new nightmare. Each time I see him he's more depressed. He is increasingly despondent about being sent to Jordan."

During the visit Mr Banna also said that letters from his children were taking up to 16 months to reach him.

Ms Teather, who has fought for Mr Banna's release, said: "Hearing that Jamil has been cleared for release should be a moment of rejoicing for his family. But instead it seems they are about to be torn apart. Jamil was arrested because of false information passed by British security services, and he has been left in Guantánamo to rot because the British government refuses to act. Now he has finally been cleared for release, the only thing that stands between this father and his family is permission from the government for him to come home."

Repugnant

Solicitor Irène Nembhard said the home secretary would be taken to court to give a guarantee that he would be allowed entry into Britain: "Since the British government had a role in his detention, to refuse him re-entry would be repugnant.

"It would be unlawful as his children are British nationals with a right to family life under article eight [of the European Convention on Human Rights]."

The government has maintained a position that it has no obligation to help British residents held by the US in Guantánamo.

A spokesman for the Pentagon refused to discuss the case and no date has been set for Mr Banna's release.