WASHINGTON – Federal enforcement of civil rights laws has dropped sharply since 1999 even though the level of complaints received by the Justice Department has remained relatively constant, according a study released Sunday.

Criminal charges alleging civil rights violations were brought last year against 84 defendants, down from 159 in 1999, according to Justice Department data analyzed by the Transactional Records Access Clearinghouse at Syracuse University.

In addition, the study found that the number of times the FBI or other federal investigative agency recommended prosecution in civil rights cases has fallen by more than one-third, from more than 3,000 in 1999 to about 1,900 last year. Federal court data also show the government has sought fewer civil sanctions against civil rights violators.

The study’s co-author, David Burnham, said the results show that civil rights enforcement dropped during President Bush’s first term in office. The Justice Department enforces a range of civil rights laws including guaranteeing fair housing access and prosecuting hate crimes.

“Collectively, some violators of the civil rights laws are not being dealt with by the government,” Burnham said. “They’ve declined by a huge number of cases. This trend, we think, is significant.”

It’s unlikely that the decline has occurred because fewer civil rights violations are occurring, the study suggests. The number of complaints about possible violations received by the Justice Department has remained level at 12,000 or so annually for each of the past five years.

Civil rights cases made up a tiny fraction of the Justice Department’s total of 99,341 criminal prosecutions in 2003. The study found, however, that only civil rights and environmental prosecutions were down from 1999 to 2003 as the total caseload rose by about 10 percent.