WASHINGTON — A top Justice Department official acknowledged yesterday that more than a half-dozen U.S. attorneys were fired in the last year, in some cases without cause, but denied Democrats’ allegations that they were dismissed and replaced for political reasons.

In testimony before the Senate Judiciary Committee, Deputy Attorney General Paul McNulty defended the department’s firing of seven U.S. attorneys since March, for reasons he would not divulge.

Mr. McNulty reminded the panel that federal prosecutors serve at the pleasure of the president. And he repeated Attorney General Alberto Gonzales’s promise to submit the name of every replacement to the Senate for confirmation.

“The attorney general’s appointment authority has not and will not be used to circumvent the confirmation process,” Mr. McNulty told the Democrat-led panel. We never have and never will seek to remove a United States attorney to interfere with an ongoing investigation or prosecution or in retaliation for a prosecution.”

Mr. McNulty spoke after weeks of Democrats’ accusations that the forced resignations of prosecutors in Arkansas and California in particular were moves to reward Republican allies.

Democrats and Republicans blamed the situation on that fact that without their knowledge a little-known provision was slipped into the Patriot Act reauthorization that took effect in March letting the attorney general replace prosecutors indefinitely. They now are seeking legislation to give interim appointment authority to District Court judges, with a deadline by which the prosecutor must be confirmed by the Senate.

Judges often are not qualified to make those appointments, Mr. Gonzales told the AP last month.

The hearing, chaired by Senator Schumer, a Democrat of New York, gave lawmakers a new chance to insist the Justice Department has used that provision to appoint political allies to U.S. attorney offices.

In Arkansas, H.E. Bud Cummins received a call from a Justice Department official last year telling him to resign and assuring him there was no cause for the firing, a fact Mr. McNulty confirmed Tuesday. Mr. Cummins’s replacement was to be J. Timothy Griffin, a former aide to presidential counselor Karl Rove and a former military prosecutor.

Also riling Democrats is the case of a former San Diego U.S. attorney, Carol Lam, whose pursuit of public corruption cases included the government’s case against Randy “Duke” Cunningham, the former Republican congressman who pleaded guilty to taking $2.4 million in bribes.

Mr. McNulty denied Ms. Lam was fired in retaliation for Cunningham’s conviction, calling Ms. Lam’s pursuit of the case “a very good thing for the American people and the Department of Justice to accomplish.”