LANHAM, Md. (WNEW/CBSNews/AP) — The head of the Senate Intelligence Committee said Tuesday the panel’s long-awaited report on brutal CIA interrogation practices used after the 9/11 terror attacks stands as a record of “a stain on our values and on our history.”

Saying her words “give me no pleasure,” Sen. Dianne Feinstein stood before the Senate to summarize the committee’s seven-year effort to uncover and evaluate the truth about CIA interrogation methods and whether they worked.

Her conclusions were unequivocal: The harsh interrogation methods didn’t work, she said, and the tactics were “far more brutal than people were led to believe.”

The California Democrat said that releasing the committee’s 500-page report was an important step toward restoring American values. She rejected the idea that the report should remain under wraps to avoid inflaming tensions around the world and with Democrats losing control of the Senate in the midterm elections, Feinstein will hand over control of the committee to the Republicans in January.

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“There may never be the right time to release this report,” she said, then quickly added: “This report is too important to shelve indefinitely.”

Releasing the report “can and does say to our people that America is big enough to admit when it’s wrong and confident enough to learn from its mistakes,” Feinstein said.

The report, she added, is “an important step to restore our values and show the world that we are in fact a just and lawful society.”

Feinstein’s committee began its study of the CIA’s interrogation practices early in 2009, and worked its way through more than 6 million pages of documents on its way to producing a 6,700 page report, which remains classified. The 500 pages released Tuesday represent an executive summary and conclusions from that longer study, which was completed in 2012.

The first three key findings of the report say that the CIA’s techniques were “not an effective means of acquiring intelligence or gaining cooperation from detainees,” that the organization’s justification for the use of the techniques rested on “inaccurate claims of their effectiveness” and that the interrogations “were brutal and far worse than the CIA represented to policymakers.”

The report goes on to list instances of sleep deprivation, water dousing and “rectal rehydration” or rectal feeding without documented medical necessity.

“The CIA reportedly led several detainees to believe they would never be allowed to leave CIA custody alive, suggesting to one that he would only leave in a coffin-shaped box,” the report says.

“Officers also threatened at least three detainees with harm to their families— to include threats to harm the children of a detainee, threats to sexually abuse the mother of a detainee, and a threat to “cut [a detainee’s] mother’s throat.”

CBS News Congressional Correspondent Nancy Cordes also reports that former President George W. Bush himself was not fully briefed on the program until 2006, and he seemed “uncomfortable” with the information he was receiving.

Read the full report on Intelligence.Senate.gov.

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