MEDICAL professionals helped the CIA perfect legal but harsh interrogation methods for terror suspects during the George W. Bush administration, according to a new report.

So-called "enhanced" questioning methods such as waterboarding were monitored and varied by medics in order to produce maximum effect while remaining within the limits established by government lawyers, according to the report released by Physicians for Human Rights.

The report described "Waterboarding 2.0" in which doctors apparently recommended adding saline to the water used to simulate drowning so as to reduce the risk of suspects falling into a coma induced by hyperhydration.

Health professionals allegedly also had a hand in monitoring sleep deprivation of up to 180 hours and experimentation on how to increase a subject's "susceptibility to severe pain".

"Any health professional who violates their ethical codes by employing their professional expertise to calibrate and study the infliction of harm disgraces the health profession and makes a mockery of the practice of medicine," lead writer of the report Dr Scott Allen said.

The group calls on US President Barack Obama to initiate a federal investigation into the claims and prosecute those responsible. It also asks Congress to amend legislation passed in 2006 that allows a "more permissive definition of the crime of illegal experimentation on detainees".

"The CIA appears to have broken all accepted legal and ethical standards put in place since the Second World War to protect prisoners from being the subjects of experimentation," said Frank Donaghue, PHR's Chief Executive Officer.

"Not only are these alleged acts gross violations of human rights law, they are a grave affront to America's core values."

Originally published as Doctors honed CIA 'torture' technique