WASHINGTON – A still-secret Senate Intelligence Committee report calls into question the legal foundation of the CIA's use of waterboarding and other harsh interrogation techniques on suspected terrorists, a finding that challenges the key defense on which the agency and the George W. Bush administration relied in arguing that the methods didn't constitute torture.

The report also found that the spy agency failed to keep an accurate account of the number of individuals it held, and that it issued erroneous claims about how many it detained and subjected to the controversial interrogation methods. The CIA has said that about 30 detainees underwent the so-called enhanced interrogation techniques.

The CIA's claim "is B.S.," said a former U.S. official familiar with evidence underpinning the report, who asked not to be identified because the matter is still classified. "They are trying to minimize the damage. They are trying to say it was a very targeted program, but that's not the case."

A portrait of evasion

The findings are among the report's 20 main conclusions. Taken together, they paint a picture of an intelligence agency that seemed intent on evading or misleading nearly all of its oversight mechanisms throughout the program, which was launched under the Bush administration after the Sept. 11, 2001, attacks and ran until 2006.

Some of the report's other conclusions, which were obtained by McClatchy, include:

• The CIA used interrogation methods that weren't approved by the Justice Department or CIA headquarters.

• The CIA impeded White House decisionmaking and oversight of the program.

• The CIA actively evaded or impeded congressional oversight of the program.

• The agency hindered oversight of the program by its own Inspector General's Office.

The 6,300-page report is the culmination of a four-year, $40 million investigation into the detention and interrogation program by the Democrat-led committee. A final draft was approved in December 2012, but it has undergone revisions. The panel voted 11-3 on April 3 to send the report's 480-page executive summary, the findings and conclusions to the executive branch for declassification before public release.

Report: CIA misled president

CIA spokesman Dean Boyd said: "Given the report remains classified, we are unable to comment."

Senate Intelligence Committee Chairwoman Dianne Feinstein added: "If someone distributed any part of this classified report, they broke the law and should be prosecuted."

The investigation determined that the program produced very little intelligence of value and that the CIA misled the Bush White House, the Congress and the public about the effectiveness of the interrogation techniques, committee members have said.

The techniques included waterboarding, which mimics drowning, sleep deprivation for up to 11 days at a time, confinement in a cramped box and slamming detainees into walls.