A leading group of doctors in the US concerned with the ethical treatment of patients has questioned the role of military psychiatrists in Quantico, Virginia, where the suspected WikiLeaks source Bradley Manning is being subjected to harsh treatment that some call torture.

The advocacy body Physicians for Human Rights has sounded the alarm over the role of psychiatrists at the brig in the marine base where Manning has been in custody since last July.

The group sees the psychiatrists as trapped in a situation of "dual loyalty", where their obligations to the military chain of command may conflict with their medical duty to protect their patient.

Christy Fujio, author of a forthcoming report on the issue, said the main concern was that psychiatrists were allowing Manning's continuing solitary confinement.

"Even if they do not officially approve it, by continuing to examine him and report back to the government on his condition, they are effectively taking part in security operations. Their failure to call it what it is, cruel and inhumane treatment, constitutes a violation of their ethical duties as doctors."

Manning has been charged with passing a mountain of digital US state secrets to WikiLeaks. He is under a prevention of injury order, or PoI, that requires him to be kept alone in a cell for 23 hours a day and to be checked every five minutes. Since earlier this month, he has also been stripped naked each night and made to parade in front of officers.

Manning himself says the conditions amount to pre-trial punishment provoked by a sarcastic remark he made to guards.

Last night, Manning's father, Brian, also denounced the way his son is being treated. He told the Frontline programme on US public television: "It's shocking enough that I would come out of our silence as a family and say, 'No, you've crossed a line. This is wrong.'" And he referred to the Guantánamo detention facility for terror suspects, saying: "They worry about people down in a base in Cuba, but here we have someone on our own soil under our own control, and they are treating him in this way".

Official records kept at the brig, released recently by Manning's lawyer, reveal that between last August and January military psychiatrists made no fewer than 16 recommendations to their military commanders that Manning should be taken off the PoI restrictions because he was no threat to himself.

Typical of the entries was that of 29 October 2010, which stated that Manning "was evaluated by the brig psychiatrist and found fit to be removed from prevention of injury classification from a psychiatric standpoint".

Only once in that five-month period did the psychiatrists conclude that the prisoner should be subjected to the restrictions. Despite the clear medical opinion given, brig commanders have repeatedly ignored the advice and retained the harsh regime. That is, Physicians for Human Rights says, an indication the US government is breaking its own clear rules.

The group's Susan McNamara, a doctor who works with victims of torture from other countries, said Manning's treatment appeared to be an extension of the interrogation tactics used against terror suspects in Guantánamo.

"That is a huge problem, as it is designed to break a person down psychologically. Solitary confinement is a form of sensory deprivation, and if you are depriving a person of the human contact they need that can amount to torture." She added: "In the US, if a patient was treated in a psychiatric hospital in the same way the military is treating Manning, the federal government would stamp all over it … [it] is disobeying its own rules."

The controversy has reached to the heart of the Obama administration. This week, state department spokesman PJ Crowley resigned, having called the confinement "ridiculous and stupid" and warned it could damage the global standing of the US. Obama himself was forced to defend the regime, saying he had been "assured" by the Pentagon it was in Manning's own interests. While the Quantico psychiatrists are given credit for having consistently argued that Manning should be removed from the current extreme regime, there are serious questions about whether they are doing enough to force change.