WASHINGTON — A program of “enhanced interrogation” used by the CIA on terrorism suspects after the 2001 attacks was far more brutal than the agency admitted and failed to secure information that foiled any threats, a U.S. Senate report said on Tuesday.

The report said the CIA misled the public and policymakers about the program, much of which was developed, operated and assessed by two outside contractors.

The report followed a five-year investigation by the Senate Intelligence Committee into the program, meant to extract information from al Qaeda and other detainees held in detention facilities around the world.

The CIA and many senior members of the U.S. administration have said the program was effective and foiled a number of terrorist plots.