WASHINGTON — A nonpartisan, independent review of interrogation and detention programs in the years after the Sept. 11, 2001, terrorist attacks concludes that “it is indisputable that the United States engaged in the practice of torture” and that the nation’s highest officials bore ultimate responsibility for it.

The sweeping, 577-page report says that while brutality has occurred in every American war, there never before had been “the kind of considered and detailed discussions that occurred after 9/11 directly involving a president and his top advisers on the wisdom, propriety and legality of inflicting pain and torment on some detainees in our custody.” The study, by an 11-member panel convened by the Constitution Project, a legal research and advocacy group, is to be released on Tuesday morning.

Debate over the coercive interrogation methods used by the administration of President George W. Bush has often broken down on largely partisan lines. The Constitution Project’s task force on detainee treatment, led by two former members of Congress with experience in the executive branch — a Republican, Asa Hutchinson, and a Democrat, James R. Jones — seeks to produce a stronger national consensus on the torture question....