Three years after the Sept. 11 attacks, more than 120,000 hours of potentially valuable terrorism-related recordings have not yet been translated by linguists at the Federal Bureau of Investigation, and computer problems may have led the bureau to systematically erase some Qaeda recordings, according to a declassified summary of a Justice Department investigation that was released on Monday.

The report, released in edited form by Glenn A. Fine, the department's inspector general, found that the F.B.I. still lacked the capacity to translate all the terrorism-related material from wiretaps and other intelligence sources and that the influx of new material has outpaced the bureau's resources.

Overhauling the government's translation capabilities has been a top priority for the Bush administration in its campaign against terrorism. Qaeda messages, saying ''Tomorrow is zero hour'' and ''The match is about to begin,'' were intercepted by the National Security Agency on Sept. 10, 2001, but not translated until days later, underscoring the urgency of the problem.

The inspector general's report on the F.B.I., the lead agency for combating domestic terrorism, said the bureau faced ''significant management challenges'' in providing quick and accurate translations.

The report offered the most comprehensive assessment to date of the F.B.I.'s problems in deciphering hundreds of thousands of intercepted phone calls, conversations, e-mail messages, documents and other material that could include information about terrorist plots and foreign intelligence matters. It revealed problems not only in translating material quickly, but also in ranking the work and in ensuring that hundreds of newly hired linguists were providing accurate translations. While linguists are supposed to undergo periodic proficiency exams under F.B.I. policy, that requirement was often ignored last year, the inspector general found in the publicly released summary of its investigation. Most of the report remains classified.

Congressional officials who have been briefed recently by the F.B.I. on the translation issue said the report offered a much bleaker assessment than the bureau has acknowledged, and leading senators from both parties denounced what they described as foot-dragging in fixing the problem.

''What good is taping thousands of hours of conversations of intelligence targets in foreign languages if we cannot translate promptly, securely, accurately and efficiently?'' asked Senator Patrick J. Leahy of Vermont, the ranking Democrat on the Judiciary Committee. ''The Justice Department's translation mess has become a chronic problem that has obvious implications for our national security.''

In its response to the report, the F.B.I. said it had taken ''substantial steps to strengthen our language capabilities,'' but it acknowledged that a shortage of qualified linguists and problems in the bureau's computer systems had led to a backlog in translating terrorism material. Robert S. Mueller III, director of the F.B.I., said he agreed ''that more remains to be done in our language services program, and we are giving this effort the highest priority.''

With $48 million in additional financing since the Sept. 11 attacks, the number of linguists at the F.B.I. rose to 1,214 as of April 2004 from 883 in 2001, with sharp increases in the number of translators of Arabic, Farsi and other languages considered critical to counterterrorism investigations. But Mr. Fine's report made clear that the expansion had not eliminated the management and efficiency problems that dogged the bureau even before Sept. 11.

The investigation blamed in part the F.B.I.'s computer systems, long derided by Congressional critics as antiquated and unwieldy. The investigation found that limited storage capacities in the system meant that older audio recordings had sometimes been deleted automatically to make room for newer material, even if the recordings had not yet been translated.

In field tests conducted by the inspector general at eight F.B.I. offices, three offices had ''Qaeda sessions that potentially were deleted by the system before linguists had reviewed them,'' the report said.