The US Senate intelligence committee approved the findings of an investigation into CIA "enhanced interrogation" — techniques the panel's leader decried as "terrible mistakes".
The committee voted nine to six to approve the 6000-page report on the former use of the tactics, which have been deemed torture by President Barack Obama and Republican Senator John McCain among others.
But they made no immediate plans to de-classify the report for the public.
Investigators pored over six million pages in a 3.5-year review of Central Intelligence Agency practice, including the sending of detainees to so-called "black sites" around the world where they endured harsh interrogation.
"I strongly believe that the creation of long-term, clandestine 'black sites' and the use of so-called 'enhanced-interrogation techniques' were terrible mistakes," Senate Intelligence Committee chair Senator Dianne Feinstein said, in a statement after the vote.
"The majority of the committee agrees."
Republicans on the panel had boycotted participation in the investigation from the start, in part because it was based on documents and not interviews conducted with intelligence agents.
The senators also probed the effects of "waterboarding," the simulated drowning technique sometimes used by US interrogators under former president George W Bush but that Obama has deemed to amount to torture.
The committee's ranking Republican, Senator Saxby Chambliss, would not say whether he voted to approve the findings. "I've already said that there are a lot of inaccuracies in it," he told reporters.
The "comprehensive review" will now get sent to the president, Feinstein said. The executive branch has until 15 February to send to the panel its comments and recommendations on declassification.
The report, said Feinstein, includes "details of each detainee in CIA custody, the conditions under which they were detained, how they were interrogated, the intelligence they actually provided and the accuracy — or inaccuracy — of CIA descriptions about the programme."
McCain, who himself was tortured as a prisoner of war in North Vietnam, said he hoped the findings would convince Americans that "torture of the kind described in this report is unworthy of our national honour and should no longer be a matter for discussion".
"The cruel, inhuman and degrading treatment of prisoners is not only wrong in principle and a stain on our country's conscience, but also an ineffective and unreliable means of gathering intelligence," McCain added.
He hoped the committee would "take whatever steps necessary to finalize and declassify this report, so that all Americans can see the record for themselves, which I believe will finally close this painful chapter for our country".
The findings come just as the film Zero Dark Thirty hits US movie theatres, promising to revive debate over the effectiveness of techniques such as waterboarding.
The film focuses on CIA agents on the hunt for terror mastermind Osama bin Laden, and depicts graphic torture scenes, including episodes of waterboarding, used — at least in the movie — to obtain information from detainees which help pinpoint Osama bin Laden's compound in Pakistan.
Feinstein and Senator Carl Levin in April released a joint statement saying coercive interrogation techniques did not play a role in locating Bin Laden.