Dennis Boyd, executive director of the National Association of Assistant United States Attorneys, which represents current federal prosecutors, told the newspaper juggling two jobs was a concern.
"I can't think of a time when there's been this many U.S. attorneys doing double duty at one time," Boyd said.
Among the attorneys spending a lot of time in Washington is Acting Associate Attorney General William Mercer, who has mostly been absent from his job as U.S. attorney in Montana for nearly two years, the Post said.
Another is Michael Sullivan of Boston, who has been in Washington for six months as acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives and is awaiting congressional confirmation.
Department of Justice spokesman Brian Roehrkasse defended the practice in a statement.
"Having U.S. attorneys serve at the department ensures that a local perspective is brought to policy-making decisions ... 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," the statement said.