WASHINGTON (CNN) -- A top Justice Department official Tuesday testified one U.S. Attorney was asked to resign without cause last year but insisted several others were told to resign for performance-related reasons.

Deputy Attorney General Paul McNulty told the Senate Judiciary Committee former U.S. Attorney H. E. "Bud" Cummins of Arkansas was asked to hand in his resignation because the Justice Department wanted to replace him with a former military prosecutor who had also worked for White House political chief Karl Rove and the Republican National Committee.

McNulty said he would inform the Committee privately why the Justice Department asked "less than ten" others to resign, but refused to discuss individual cases publicly.

At the hearing called by angry Democratic Senators, Sen. Charles Schumer, D-New York, blasted the Justice Department over allegations several top federal prosecutors had been removed for political reasons.

"I have never seen the Department more politicized," Schumer declared. "It appears even the hiring and firing of our top federal prosecutors has become infused and corrupted with political rather than prudent considerations," he said.

McNulty, who has known Schumer for many years, said he takes the charges personally.

"It is like a knife in my heart," he said.

"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," McNulty said.

Democratic Senators led by Diane Feinstein, D-California, have questioned the removal of U.S. Attorney Carol Lam in San Diego, who led the bribery investigation of convicted former Congressman Randy "Duke" Cunningham.

McNulty said there were other reasons for Lam's dismissal but would disclose the reasons only in a private session. Lam had been criticized by Republican lawmakers for failure to aggressively prosecute alien smugglers along the Southwest Border.

The Deputy Attorney General promised the committee the Department will not attempt to circumvent the Senate confirmation process through use of interim appointments, and will formally nominate all interim U.S. Attorneys.