HELENA, Mont. (AP) - Montana's U.S. attorney, who also is the acting No.3 official at the Justice Department in Washington, D.C., engineered a rule change allowing federal prosecutors to live outside their districts to hold other jobs, The Washington Post reported Wednesday.

A call seeking comment from Bill Mercer, the attorney with dual roles, was not immediately returned on Wednesday.

The Post reported that on Nov. 10, 2005, Attorney General Alberto Gonzales wrote U.S. District Judge Donald Molloy of Montana that Mercer was not violating federal law by largely spending his time in Washington as a senior aide to Gonzales.

On the same day, Mercer directed a staffer for Sen. Arlen Specter, R-Pa., to place in a bill language changing rules so federal prosecutors could live outside their districts to hold other jobs, according to the newspaper. Several months later, Congress passed the provision in reauthorizing the USA Patriot Act, legislation Mercer was assigned to shepherd, the Post reported.

The staffer, Brett Tolman, is now the U.S. attorney for Utah. He did not return a call seeking comment Wednesday.

In a letter on Oct. 20, 2005, Molloy complained about Mercer's absence from Montana and said he was violating federal law. Gonzales responded on Nov. 10, 2005, that Mercer met residency requirements for the attorney position.

The Post reported that Justice Department spokesman Brian Roehrkasse declined to comment on Mercer's role in the legislation, nor would Roehrkasse discuss what Gonzales knew about the measure at the time he wrote Molloy.

Another spokesman, Dean Boyd, said in a statement Wednesday that "any suggestion that Bill's performance of dual roles failed to comply with the law is flat wrong."

The Justice Department has a long-standing practice of allowing prosecutors to serve in temporary positions, the spokesmen said, and the bill's amendment clarifies that residency requirements do not preclude working in two places.

Mercer has been nominated for a permanent appointment as associate attorney general, the position he now holds temporarily. He is one of about six U.S. attorneys who are in Washington to work in senior Justice Department jobs.

Sen. Jon Tester, D-Mont., on Wednesday called for Mercer to resign as Montana's chief federal prosecutor.

"Mr. Mercer was operating outside federal law, so he had the law changed," Tester said. "That might work in Alberto Gonzales' Justice Department, but it's not how we do business in Montana."

The state's senior senator, Democrat Max Baucus, said Mercer "is not serving the public by trying to wear two hats."

"He needs to choose which job he wants and give it 100 percent," Baucus said.

Boyd said Mercer has served effectively as both Montana's attorney and as acting associate attorney general. It is time the Senate act on the nomination that has been pending for eight months, Boyd said.

"If members of the Senate do in fact have concerns about his dual service, we would hope they would act on his confirmation and he will resign his post as U.S. attorney, alleviating their concerns," Boyd said.