An analysis of Justice Department data by the Transactional Records Access Clearinghouse at Syracuse University in New York found almost 19,000 prosecutions were credited to the FBI in 2001, but in 2006 that number fell to 12,700.
During that same five-year period, terrorism prosecutions rose 26 percent, the Christian Science Monitor reported Thursday.
Of the various types of prosecutions, organized crime fell by 73 percent between 2000 and 2006, while pornography cases doubled from 385 cases in to 2000 to 796 in 2006, the report said.
The ratio of drug prosecutions remained the same, although fewer in number, the TRAC analysis found -- 5,014 in 2000 and 2,380 in 2006.
The shift in priorities is alarming to Lee Hamilton, vice chairman of the Sept. 11 commission.
"There's an awful lot of malfeasance in this country at high levels: You've got drug dealers, and ordinary criminals, and all the rest, and they need to be prosecuted," Hamilton told the Monitor.