The last remaining British detainee at the Guantanamo Bay prison has gone on hunger strike and said in a letter obtained by the BBC on Friday that he is being treated inhumanely.

Shaker Aamer has been held at the US-run prison in Cuba for almost 10 years despite being cleared for release in 2007 when the administration of then-US president George W. Bush acknowledged it had no evidence against him.

He was captured in Jalalabad, Afghanistan, in December 2001 and taken to Guantanamo two months later.

The British government continues to call for his release.

Aamer, who was born in Saudi Arabia but has British residency, wants to be freed or sent for a "just and public" trial.

His wife and two children live in London.

In a letter obtained by BBC radio and written and signed by Aamer and seven other detainees, he alleges he has been treated inhumanely during his detention.

He wrote: "Inhumane treatment is taking place at the hospital among other areas, especially affecting the sick and those who are on (hunger) strike and our deprivation of real treatment, health, diet and appropriate clothing which are not provided to us, nor we are allowed to provide them for ourselves."

In the letter, he describes himself, and fellow detainees, as "hostages."

He calls for their cases to be considered "as soon as possible", adding: "Give us the right to a just and a public trial or set us free without conditions."

The WikiLeaks website has obtained a file suggesting Aamer is one of the key leaders inside Guantanamo, organises hunger strikes and was a "close associate" of Osama bin Laden.

Alistair Burt, a junior minister in the Foreign Office, said: "We have been making significant representations to the United States over a period of time.

"The prime minister has raised it, the foreign secretary has raised it, our officials have raised it.

"It's a matter for the United States to release Shaker Aamer who is a legal UK resident, and we continue to make what representations we can.

"It is a matter for the United States authorities to take the decision to release."

US President Barack Obama promised to close Guantanamo when he came to power, but three years later it remains open.

The camp's highest-profile detainee is 9/11 mastermind Khalid Sheikh Mohammed. He and four alleged co-conspirators face military trials which are expected to start later this year.