A British resident being held in Guantanamo Bay should be released because of his "fragile medical condition", a group of senior doctors have said.
Shaker Aamer is suffering from post-traumatic stress disorder (PTSD) and asthma and his continued detention is having an "appalling effect" on his health, according to the medics.
David Cameron is expected to raise Mr Aamer's case with US President Barack Obama during a visit to Washington this week.
In a letter organised by consultant neurologist and human rights activist David Nicholl, health experts - including consultants and professors - said Mr Aamer has "pressing medical concerns".
Mr Aamer, who is originally from Saudi Arabia but moved to south London, where his British wife and family still live, has been held in Guantanamo Bay since 2002.
He is accused of being a close associate of Osama bin Laden - a charge he denies.
US authorities have threatened to send him back to Saudi Arabia despite his British residency.
The letter, written to the Daily Mail, said he had his "first independent medical assessment that revealed he was suffering from post-traumatic stress disorder, asthma, oedema and chronic urinary retention".
The doctors called for Mr Aamer to be returned to the UK.
They added: "We would point out that Shaker's ongoing detention without trial is having an appalling effect not just on his health, but those of his family, especially his wife - all of whom are British citizens."
Separately, five Yemenis have been freed from Guantanamo and sent to Estonia and Oman, US officials said.
All five were captured in Pakistan and detained by the US as suspected al Qaeda fighters. US officials later determined it was no longer necessary to detain them but have struggled to find other countries willing to take them in.
Four of the men went to Oman and one to Estonia, according to a Pentagon statement.
