onlineredaktion - As evidence of prisoner mistreatment at Guantanamo Bay began to mount in 2002, FBI agents at the base created a "war crimes file" to document accusations against American military personnel, but were eventually ordered to close the file down, a Justice Department report has disclosed.

The report, a 437-page review prepared by the Justice Department inspector-general, provides the fullest account to date of internal dissent and confusion within the Bush Administration over the use of harsh interrogation tactics by the military and the Central Intelligence Agency.

In one of several previously undisclosed episodes, the report found that US military interrogators appeared to have collaborated with visiting Chinese officials at Guantanamo Bay to disrupt the sleep of Chinese Muslims held there, waking them every 15 minutes the night before their interviews by the Chinese. In another incident, a female interrogator reportedly bent back an inmate's thumbs and squeezed his genitals as he grimaced in pain. The report describes what one official called "trench warfare" between the FBI and the military over methods used on prisoners.

The report says that officials at senior levels at the FBI, the Justice Department, the Defence Department and the National Security Council were all made aware of the complaints of FBI agents, but little was done.

The report quotes passionate objections from FBI officials, who grew increasingly concerned about practices like intimidating inmates with snarling dogs, parading them in the nude before female soldiers, or "short-shackling" them to the floor for hours in extreme heat or cold. Such tactics, said one FBI agent in an email to supervisors in November 2002, might violate US law banning torture.

"Beyond any doubt, what they are doing (and I don't know the extent of it) would be unlawful were these enemy prisoners of war," Spike Bowman, head of the FBI's national security law unit, wrote in July 2003. In 2003 an FBI official ordered the "war crimes file" closed, because "investigating detainee allegations of abuse was not the FBI's mission".

FBI officials, including Pasquale D'Amuro, then the bureau's top counterterrorism officer, believed the physical pressure being used by the CIA was less effective than non-coercive methods, and "was wrong and helped al-Qaeda in spreading negative views of the United States", the report says.

The inspector-general, Glenn Fine, found that in a few instances, FBI agents participated in interroga-tions using tactics that would not have been permitted in the US. But the "vast majority" of agents followed FBI legal guidelines and "separated themselves" from harsh treatment, the report says.