The CIA carried out "brutal" interrogations of terror suspects in the years after the 9/11 attacks on the US, a US Senate report has said.
The summary of the report, compiled by Democrats on the Senate Intelligence Committee, said that the CIA misled Americans about what it was doing.
The information the CIA collected this way failed to secure information that foiled any threats, the report said.
President Obama said the methods used were inconsistent with US values.
"These techniques did significant damage to America's standing in the world and made it harder to pursue our interests with allies and partners," he said in a statement.
Reacting to the release of the report summary, the Senate Republican leaders insisted that the methods used helped in the capture of important suspects and the killing of Osama bin Laden.
"Claims included in this report that assert the contrary are simply wrong," Senators Mitch McConnell and Saxby Chambliss said in a joint statement.
The Senate committee's report runs to more than 6,000 pages, drawing on huge quantities of evidence, but it remains classified and only a 480-page summary has been released.
Publication had been delayed amid disagreements in Washington over what should be made public.
President Barack Obama halted the CIA interrogation programme when he took office in 2009.
Earlier this year, he said that in his view the methods used to question al-Qaeda prisoners amounted to torture.
During the presidency of George W Bush, the CIA operation against al-Qaeda - known internally as the Rendition, Detention and Interrogation programme - saw more than 100 suspected terrorists held in "black sites" outside the US.
They were interrogated using methods such as waterboarding, slapping, humiliation, exposure to cold and sleep deprivation.