Medical staff tasked with monitoring the health of prisoners held by the United States in Guantanamo Bay, secret CIA prisons and in Afghanistan were complicit in abuses against them, an independent report has said.

The US Department of Defence and the CIA demanded that the healthcare personnel "collaborate in intelligence gathering and security practices in a way that inflicted severe harm on detainees in US custody", according to the two-year study by the Institute of Medicine and the George Soros-funded Open Society Foundations.

Medical professionals helped design, enable and participated in "torture and cruel, inhumane and degrading treatment" of detainees, according to the report released on Monday.

Collaboration at US prisons in Afghanistan, Guantanamo and secret prisons run by the CIA began after the September 11, 2001 attacks in the United States.

"It's clear that in the name of national security ... physicians were transformed into agents of the military and performed acts that were contrary to medical ethics and practice," said study co-author Gerald Thomson, professor of medicine emeritus at Columbia University.

Investigation urged

The report, conducted by two dozen military, ethics, medical, public health and legal experts, calls on the US Senate Intelligence Committee to fully investigate medical practices at the detention sites.

It's important to underscore that the CIA does not have any detainees in its custody and President Obama terminated the Rendition, Detention and Interrogation Program by executive order in 2009. Dean Boyd,

CIA public affairs chief

Co-author Leonard Rubenstein of Johns Hopkins University focused on force-feeding Guantanamo Bay's hunger strikers, as well as CIA agents' use of harsh interrogation methods and simulated drowning known as waterboarding at secret sites.

"Abuse of detainees and health professional participation in this practice is not behind us as a country," he told the AFP news agency.

Both the CIA and the Pentagon rejected the report's findings.

The report "contains serious inaccuracies and erroneous conclusions", said CIA public affairs chief Dean Boyd.

"It's important to underscore that the CIA does not have any detainees in its custody and President [Barack] Obama terminated the Rendition, Detention and Interrogation Programme by executive order in 2009," Boyd said.

Obama signed an executive order shortly after taking office in 2009 that banned interrogation techniques used under George W Bush, which critics say amount to torture.

Although the president has not banned extraordinary rendition, new rules prevent suspects from being tortured before they are transferred to a different country for interrogation, trial or continued detention.

Obama also established a task force to review interrogation and transfer policies and issue recommendations, but the group's 2009 report remains classified.

'Extraordinarily violent patients'

At the Pentagon, spokesman Todd Breasseale said that none of the critics of prisoner care "have had actual access to the detainees, their medical records", or the procedures at the Guantanamo detention camp.

According to Breasseale, Guantanamo's doctors and nurses are "consummate professionals working under terrifically stressful conditions, far from home and their families, and with patients who have been extraordinarily violent".

He added that the medical staff "routinely provide not only better care than any of these detainees have ever known, but care on par with the very best of the global medical profession".