A group of senior doctors has called for a London man held in Guantanamo Bay to be released, warning of his "fragile medical condition".
Medics said that Shaker Aamer was suffering from conditions including post-traumatic stress disorder and asthma and his continued detention was having an "appalling effect" on his health and that of his family.
Prime Minister David Cameron is expected to again raise Mr Aamer's case with President Barack Obama during his visit to Washington this week.
Mr Aamer, who is originally from Saudi Arabia but moved to Battersea, London, and has a wife and four children there, has been incarcerated at the controversial US detention centre since 2002.
In a letter to a national newspaper, the health experts, including consultants and professors, said Mr Aamer had "pressing medical concerns".
The signatories include three members of the Foreign Office pro bono medical panel, which can assist with advice for Britons held overseas but which the doctors said had so far not been allowed to help Mr Aamer.
The letter was organised by David Nicholl, a consultant neurologist, human rights activist and member of the council of the Royal College of Physicians, and is signed by physicians, including professors of neurology and public health, consultants and GPs.
Cori Crider of the campaign group Reprieve has called on the Foreign Secretary William Hague to do more to ensure the release of Shaker Aamer, the Londoner who is still being held in Guantanamo Bay.
The director of the legal charity Reprieve has urged the UK Government to do more to help Shaker Aamer.
A South Londoner who is being held in the US detention camp in Guantanamo Bay has gone on hunger strike. Shaker Aamer has been held at the base for eleven years but has not been tried or charged.
Mr Aamer has said he has lost over 30 pounds since he joined the strike. Lawyers for the inmates say around three-quarters of them have gone on hunger strike at the camp.