Worst of all, the report found, was the inability of the C.I.A. to investigate itself. It was not Soviet deception that allowed Mr. Ames, a drunken and bumbling spy, to flourish as long as he did, the report said. It was the agency's own self-deception -- its behavior as "a bureaucracy which was excessively tolerant of serious personal and professional misconduct among its employees," which denied or ignored problems ranging from blown operations to third-rate workers.

The agency's long failure to root out the traitor in its midst "led to the loss of virtually all of C.I.A.'s intelligence assets targeted at the Soviet Union at the height of the cold war," the committee said. Ten Soviet and Eastern European agents were executed by Moscow, more than 100 intelligence operations run by the United States and its allies were exposed and thousands of pages of secret documents were lost, the report said.

Three former directors of central intelligence -- the late William J. Casey, William H. Webster and Robert M. Gates, who was acting director in 1987 -- were responsible for an "incomprehensible" failure to undertake a serious investigation of the case in the 1980's, the panel said.

Its members also unanimously criticized the current director, R. James Woolsey, for failing to dismiss, demote or suspend anyone now serving with the agency for the self-inflicted wounds of the misguided mole hunt.

Mr. Woolsey has said he is working as hard as he can to change the culture of the C.I.A. In prior interviews, Mr. Webster has said the hunt for the spy went well when he was director from 1987 to 1991, despite "not being able to account for things happening," and Mr. Gates has said the agency's senior managers did not know the full scope of the problem when he was acting director in 1987. Mr. Gates was not criticized for his handling of the investigation when he was director from 1991 to 1993.