A doctor is to run the London Marathon in an orange Guantanamo Bay-style boiler suit to highlight the plight of UK residents still held there.
Dr David Nicholl says most of the residents had "justified asylum"
Dr David Nicholl is leading calls for government action over at least five men still held at the US base in Cuba.
It comes after Dr Nicholl and relatives of the men, who are not UK citizens, delivered a letter from Amnesty International to Downing Street.
The government says it can only help people with UK citizenship.
Dr Nicoll, a consultant neurologist at Queen Elizabeth Hospital and City Hospital, Birmingham, hopes to raise awareness of the men's plight at Sunday's marathon.
"It is an international disgrace that none one of these people have gone through any due process in the last three years," he said.
"I would emphasise that I am running for justice, I am not running for terrorists.
"If democracy means anything, it means having a proper due process. If these people are guilty they should be convicted, if they are innocent they should be freed."
Dr Nicholl, 40, told BBC News that although those held were not British citizens, most were asylum seekers who had been given "justified asylum".
About 500 people are still being held at the Cuban jail
He mentioned the case of Iraqi Bisher al-Rawi, who he said was tortured under Saddam Hussein's regime.
He said Mr al-Rawi had lived in the UK for more than 20 years and his children were British.
Mike Blackmore, media director for Amnesty, said the men were relying on the government's help.
"Amnesty is concerned about all 500 detainees still being held in Cuba," he said.
"But we are particularly concerned these residents will be forgotten men and we think the government has a moral responsibility, if not a legal responsibility, to help them."
A Foreign Office spokeswoman said: "Our position remains that the British government is not in a position to give consular or diplomatic help to non-British nationals."
However, she added that foreign office minister Baroness Symons had met with some relatives of the UK residents being held to explain the government's position and to hear their concerns.
In January, four British men held at Guantanamo Bay for three years as "enemy combatants" were freed by UK police after questioning.