CHAPEL HILL, N.C. -- Democratic presidential candidate John Edwards on Wednesday called on President George W. Bush to fire political adviser Karl Rove if he refuses to testify under oath about alleged illegal activity within the executive branch.

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Edwards accused Rove of working with Attorney General Alberto Gonzales to play politics within the Department of Justice. Congressional Democrats are investigating whether politics played an improper role in the firing of eight U.S. attorneys.

"The President should demand that Alberto Gonzales resign, and he should fire Karl Rove. They have turned the Department of Justice into the Department of Political Payback. In doing so, they deny every American the legitimate expectation that justice will be administered without reference to partisan considerations," Edwards said in a prepared statement.

"If President Bush doesn't have the courage to fire Gonzales, he should step up and resign for the good of the country.

"And with a new investigation aimed squarely at Karl Rove, the President should fire him if he continues to refuse to testify under oath. New reports that federal employees were urged to assist Republican candidates through their official duties are outrageous. This is the American people's government, not the Republican Party's," Edwards said.

The U.S. Office of Special Counsel has also launched a probe into allegations that executive branch employees violated federal laws by using their positions to advocate for the Republican Party.

White House Counsel Fred Fielding has refused to allow congressional investigators to question Rove under oath or on the record. Fielding has also protected former White House counsel Harriet Miers and other White House staff members.