More than 260 doctors from around the world have called on the US to stop force-feeding hunger strikers at Guantánamo Bay.
They say international agreements prevent doctors from force-feeding if individuals have made an informed choice about their protest.
The restraint chairs used to hold inmates while feeding tubes are inserted, which are reportedly used at the US military base in Cuba, are also banned, they say.
An estimated 500 people are being held without trial at the base in Cuba.
The US has argued that the Geneva convention does not apply to prisoners as they are "enemy combatants" who continue to pose a threat to national security.
A total of 263 doctors from Britain, Ireland, the US, Germany, Australia, Italy and the Netherlands signed a joint letter published in this week's edition of The Lancet medical journal.
The signatories, including best-selling British author Oliver Sacks, say the doctors who are carrying out the actions at the camp should be disciplined by their professional bodies.
Dr David Nicholl of City hospital, Birmingham, who coordinated the action, said: "This letter really shows the strength of feeling amongst the world's leading medical experts.
"They are saying with one voice that force-feeding of hunger strikers by medical staff at Guantánamo is unequivocally wrong.
"We urge the US government to ensure that detainees are assessed by independent physicians and that techniques such as force-feeding and restraint chairs are abandoned forthwith in accordance with internationally agreed standards."
Co-signatory Dr William Hopkins, a psychiatrist from the Medical Foundation for the Care of Victims of Torture, said: "Doctors force-feeding prisoners at Guantánamo are acting as an arm of the military and have abrogated their medical-ethical duties.
"The American Medical Association should launch disciplinary proceedings against any of its members known to have participated in violating prisoners' rights in this way."
The World Medical Association specifically prohibits force-feeding in the declarations of Tokyo and Malta, to which the American Medical Association is a signatory.
More than 80 inmates are believed to have gone on hunger strike late last year, a figure that has now reportedly dropped to four or five.
Amnesty International said one of the detainees reportedly continuing the hunger strike is Shaker Aamer, a Saudi national who is a British resident married to a British woman.
Kate Allen, the group's UK director, called for independent medical examination of the prisoners.
"This letter must be acted on. Rather than trying to break the hunger strike by forcibly feeding the detainees, the US should respect their human rights by putting an end to arbitrary detention and ensuring access to justice," she said.