The leading American professional group for psychologists secretly worked with the Bush administration to help justify the post-9/11 US detainee torture program, according to a watchdog analysis released on Thursday.

The report, written by six leading health professionals and human rights activists, is the first to examine the alleged complicity of the American Psychological Association (APA) in the “enhanced interrogation” program.

Based on an analysis of more than 600 newly disclosed emails, the report found that the APA coordinated with Bush-era government officials – namely in the CIA, White House and Department of Defense – to help ethically justify the interrogation policy in 2004 and 2005, when the program came under increased scrutiny for prisoner abuse by US military personnel at the Abu Ghraib prison in Iraq.

A series of clandestine meetings with US officials led to the creation of “an APA ethics policy in national security interrogations which comported with then-classified legal guidance authorizing the CIA torture program,” the report’s authors found.

The APA is the largest organization representing psychologists in the US, with more than 122,500 members. That mental health professionals – let alone members of the APA itself – played any role in the justification or enhancement of the interrogation program undoubtedly lent the program an air of legitimacy, if even behind closed doors.

In secret opinions, the US Department of Justice argued that the torture program did not constitute torture and was therefore legal, since they were being monitored by medical professionals.

A spokeswoman for the APA denied that the group had coordinated its actions with the government, in a statement to the New York Times. There “has never been any coordination between the APA and the Bush administration on how APA responded to the controversies about the role of psychologists in the interrogations program”, Rhea Farberman said.

However, the report details a meeting in July 2004 – as images from Abu Ghraib stirred international outrage – at which the APA invited psychologists “directly involved in the CIA’s ‘enhanced’ interrogation program” to meet with the APA’s ethics office regarding the organization’s ethics policies. The meeting came on the heels of a secret order – signed one month prior by then-CIA director George Tenet – suspending the agency’s use of torture techniques, which also requested a detailed policy review.

A second meeting took place in 2005, when the APA Presidential Task Force on Psychological Ethics and National Security (Pens), according to the emails, ensured that the “legal safeguards built into the ‘torture memos’ issued by the DOJ’s office of legal counsel were codified in APA ethics policy”.

Following the Pens meeting, the report says the APA passed “extraordinary policy recommendations”, in which the association reaffirmed that its members could be involved in the interrogation program, without violating APA ethical codes.

Additionally, the APA permitted research on “individuals involved in interrogation processes” without their consent; according to the report’s authors, such a policy turned against decades of medical ethics prohibitions.

“The analysis presented in this report raises serious concerns about the APA Board’s knowledge of, involvement in and responsibility for allowing the US government to unduly influence and change APA policy on interrogations,” the report concludes. “The resulting policy facilitated the continuation of the Bush administration torture program.”

Although the Bush-era torture program has since been shuttered, a partially declassified report released by the Senate intelligence committee in December concluded that torture does not work. Detainees subjected to so-called enhanced techniques, it found, produced no intelligence or “fabricated information, resulting in faulty intelligence”.

Donna McKay, the executive director of Physicians for Human Rights (PHR), an organization with which all of the report’s authors have been affiliated at some point, said in a statement issued on Thursday: “This calculated undermining of professional ethics is unprecedented in the history of US medical practice and shows how the CIA torture program corrupted other institutions in our society.”

PHR has previously called on the APA to clarify its ties to the CIA torture program and its architects, namely the two CIA contract psychologists Dr James Mitchell and Dr Bruce Jessen. “In the meantime,” the statement said, “there is sufficient evidence of wrongdoing to warrant a Department of Justice investigation.”

In their own report, issued last December, PHR called for a federal commission to investigate the full extent of health professionals’ alleged participation in CIA torture, accusing them of “[betraying] the most fundamental duty of the healing professions” and suggesting that some psychologists may have committed war crimes.

The new report found that the APA concealed its numerous contacts with Mitchell and Jessen, and had failed to disclose Mitchell’s past APA membership when it released its 2007 statement in response to public revelation of Mitchell’s role in enhanced interrogations.

Perhaps most damning, the watchdogs reported that in examining the trove of 638 new emails, they found no evidence that any APA staff member “expressed concern over mounting reports of psychologist involvement in detainee abuse during four years of direct email communications with senior members of the US intelligence community.”

Last November, the APA announced an independent investigation into its alleged collusion with the CIA. The findings are expected this summer.