LONDON — Britain’s intelligence services tolerated and abetted “inexcusable” abuse of terrorism suspects by their American counterparts, according to a report released by Parliament on Thursday that offers a wide-ranging official condemnation of British intelligence conduct in the years after the Sept. 11, 2001, attacks.

Many cases described by Parliament’s Intelligence and Security Committee involved British agents feeding information to allies, primarily Americans, for the interrogation of detainees who they knew or suspected were being abused, or receiving intelligence from such interrogations, without raising objections.

The committee documented dozens of cases in which Britain participated in sending suspects to other countries that were known to use torture or aided others in doing so — a practice known as rendition. But it said that in four years of investigation, reviewing some 40,000 documents, it found only two instances of British agents directly taking part in abuse.

The report also says that considerable evidence makes it “difficult to comprehend” how top officials in London “did not recognize in this period the pattern of mistreatment by the U.S.” — abuses that the Intelligence Committee of the United States Senate has documented in grisly detail, and, in many cases, categorized as torture.