A half-dozen sitting U.S. attorneys also serve as aides to Attorney General Alberto R. Gonzales or are assigned other Washington postings, performing tasks that take them away from regular duties in their districts for months or even years at a time, according to officials and department records.

Acting Associate Attorney General William W. Mercer, for example, has been effectively absent from his job as U.S. attorney in Montana for nearly two years -- prompting the chief federal judge in Billings to demand his removal and call Mercer's office "a mess."

Another U.S. attorney, Michael J. Sullivan of Boston, has been in Washington for the past six months as acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives. He is awaiting confirmation to head the agency permanently while still juggling his responsibilities in Massachusetts.

The number of U.S. attorneys pulling double duty in Washington is the focus of growing concern from other prosecutors and from members of the federal bench, according to legal experts and government officials.

The growing reliance on federal prosecutors to fill Washington-based jobs also comes amid controversy over the firings of eight other U.S. attorneys last year. One of them, David C. Iglesias of New Mexico, was publicly accused by the Justice Department of being an "absentee landlord" who was away from his job too much.

"I can't think of a time when there's been this many U.S. attorneys doing double duty at one time," said Dennis Boyd, executive director of the National Association of Assistant United States Attorneys, which represents current federal prosecutors.

Justice spokesman Brian Roehrkasse characterized the fact that U.S. attorneys were filling other Washington-based Justice jobs as both unremarkable and beneficial. He cited four examples of chief prosecutors who also served stints in the deputy attorney general's office during the George H.W. Bush administration, and two similar examples during the Clinton years.

"Having U.S. attorneys serve at the department ensures that a local perspective is brought to policy-making decisions," Roehrkasse said in a statement. ". . . U.S. Attorneys assigned to the Department's headquarters also gain a national perspective and can bring this perspective and national focus to their districts."

But Boyd said the prolonged absence of a chief prosecutor can lead to a lack of direction and leadership in U.S. attorneys' offices. The Justice Department made a similar argument in defending the firing of Iglesias, alleging that he had entrusted too much responsibility to his first assistant.

"Quite frankly, U.S. attorneys are hired to run the office, not their first assistants," William E. Moschella, the principal associate deputy attorney general, told the House Judiciary Committee last month.

Iglesias filed a complaint with federal investigators last week, alleging that his dismissal amounted to discrimination based on his status as an officer in the Navy Reserve, which took him away from the job for 40 to 45 days a year. Alleged absenteeism has been the Justice Department's main public criticism of Iglesias, although officials have more recently added concerns about his handling of voter fraud and immigration cases to their arguments about him.

"It's a double standard and it's hypocritical," Iglesias said. "Not one judge from my district wrote a letter to main Justice saying I was gone too much. . . . Most of my absences were military-related."