The family of a Brighton law student detained at Guantanamo Bay has handed a petition for his release to the American ambassador in London.
Omar Deghayes fled to the UK from Libya in the 1980s
Omar Deghayes, 36, has been imprisoned at the US military base in Cuba since his arrest in Pakistan in 2002.
He is accused of committing terrorist activities against the United States.
The detainee's lawyer, Clive Stafford-Smith, said his client was "immensely depressed" and had been on hunger strike for 17 weeks.
The American authorities claim Mr Deghayes is a Chechen rebel and say they have video footage of him brandishing a Kalashnikov.
But Mr Stafford-Smith said it was a case of mistaken identity.
"We can prove the videotape they have is not Omar - it is a Chechen rebel who died in April 2004," he said.
Mr Deghayes' supporters took heart from the Prime Minister who, before a parliamentary committee on Tuesday, said he thought the camp should be closed down.
"I think it is an anomaly and you can't maintain it forever... It is a difficult situation but most people recognise at some point it must be brought to an end."
Other campaigners fighting for the release of Mr Deghayes include his local Brighton MP Des Turner.
"It's appalling that a country that is the self-appointed leader of the free world should deny human rights on a massive scale.
"I am very glad that Tony has finally come out and condemned the existence of Guantanamo Bay," Mr Turner added.
Mr Deghayes was granted refugee status in the UK after fleeing Libya with his family in the 1980s when his father was assassinated.