WASHINGTON — The Senate Intelligence Committee has asked the C.I.A. for an internal study done by the agency that lawmakers believe is broadly critical of the C.I.A.’s detention and interrogation program but was withheld from congressional oversight committees.

The committee’s request comes in the midst of a yearlong battle with the C.I.A. over the release of the panel’s own exhaustive report about the program, one of the most controversial policies of the post-Sept. 11 era.

The Senate report, totaling more than 6,000 pages, was completed last December but has yet to be declassified. According to people who have read the study, it is unsparing in its criticism of the now-defunct interrogation program and presents a chronicle of C.I.A. officials’ repeatedly misleading the White House, Congress and the public about the value of brutal methods that, in the end, produced little valuable intelligence.

Senator Mark Udall, Democrat of Colorado, disclosed the existence of the internal C.I.A. report during an Intelligence Committee hearing on Tuesday. He said he believed it was begun several years ago and “is consistent with the Intelligence’s Committee’s report” although it “conflicts with the official C.I.A. response to the committee’s report.”