A nonpartisan panel has concluded that it was “indisputable” that terrorist suspects were tortured by the United States in the years after the September 11, 2001 attacks, with the knowledge of the U.S. president, according to the study released on Tuesday.

The report looked at U.S. practices in Iraq, Afghanistan and at the Guantanamo Bay prison in Cuba. It also examined the CIA’s rendition programme, naming other countries that cooperated including Britain, Canada, Italy, Germany, Sweden, Egyt, Syria, Morocco and Jordan.

The report was researched and written by an 11-member task force led by former congressmen Asa Hutchinson, a Republican, and James Jones, a Democrat. The task force was convened by the Constitution Project, a non-profit think-tank committed to building bipartisan agreement on constitutional questions.

The report said the U.S. rendition programme, in which suspects were captured in one country and transferred to another for questioning under the radar of international legal norms, was unjustified and counterproductive and damaged the country’s reputation.

The CIA operated secret prisons within three European countries: Poland, Lithuania and Romania. Poland and Lithuania have acknowledged their existence, but Romania continues to deny that a secret prison existed there.

It has been known for several years that the CIA used waterboarding, kept prisoners in stress positions and deprived them of sleep.

But the report aimed to end the debate over whether these practices constitute torture. During the George W Bush administration, a top government lawyer defined torture as physical pain equivalent to the pain of “organ failure” or “even death.” Anything short of that was not considered torture during the Bush administration.

The report said in the U.S.’s many previous conflicts, there is little doubt that some U.S. personnel committed brutal acts against captives.

“But there is no evidence there had ever before been the kind of considered and detailed discussions that occurred after September 11, directly involving a president and his top advisers on the wisdom, propriety and legality of inflicting pain and torment on some detainees in our custody,” the report said.

The report also concluded that when torture was used it resulted in very little usable intelligence.

The task force examined the federal government’s policies and actions related to the capture, detention and treatment of suspected terrorists during the Clinton, Bush and Obama administrations.

The 577-page report, which took more than two years to research and compile, is based on public records and interviews with more than 100 people, including former detainees, military and intelligence officers, interrogators and policymakers, the introduction to the report said.

Members of the task force staff conducted on-the-ground fact-finding in Afghanistan, Iraq, Libya, Lithuania, Poland and the U.K. and Guantanamo Bay.

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