Human rights group Amnesty has renewed calls for long-term British residents detained in Guantanamo Bay in Cuba to be released.
Omar Deghayes fled to the UK from Libya in the 1980s
It claims nine detainees have been UK residents, although no UK nationals are now held at the US naval base.
The British Government has said it cannot represent people who choose not to seek British citizenship.
But Amnesty, highlighting the case of a Brighton man held since 2002, said the reluctance to act was shameful.
The group's UK director Kate Allen said: "These men have become forgotten prisoners.
"After four years, Guantanamo has become a byword for abuse and an indictment of the US government's failure to uphold human rights in the war on terror."
'No special treatment'
Brighton student Omar Deghayes, 36, has been held at Guantanamo for three years.
He was arrested in Pakistan and accused of committing terrorist acts against the United States, but his lawyers claim it is a case of mistaken identity.
Mr Deghayes was born in Libya, but fled the country in the 1980s when his father was assassinated and was granted refugee status in the UK, where he was educated and applied for British citizenship.
His sister, Amani Deghayes, who is campaigning for his release, said: "I am not looking for any special treatment for my brother. I just want his basic human rights to be respected.
"What disappoints me most is the unwillingness of the UK government to lift a finger."