A former Senate staffer filed a federal lawsuit Monday to stop an investigation into how Republicans obtained computer memos taken from Democrats' machines.

Manuel Miranda (searchasked the U.S. District Court for the District of Columbia to stop a Justice Department and Secret Service investigation into whether a crime was committed when he and another of Sen. Orrin Hatch's former employees got Democratic documents from a computer server shared by both sides. Miranda worked for the Senate Judiciary Committee (search), of which Hatch, R-Utah, is chairman.

Miranda said in papers filed Monday that the investigation was solely to hide senators' own wrongdoing.

"Senators used all their official power and their influence over the press to disguise their own wrongdoing, by systematically accusing plaintiff of escalating degrees of criminality," the pleading said.

At the same time, it said, "Other senators failed to defend the plaintiff, a loyal staff aide, and failed to address the apparent misconduct of their Senate colleagues, appearing more interested in avoiding criticism to themselves."

Named as defendants were Attorney General John Ashcroft (search) and Ralph Basham, director of the Secret Service (search).

A Justice Department spokesman refused to comment. A call to the Secret Service was not immediately returned.

The court should "issue a preliminary and permanent injunction enjoining defendants, their employees, agents, grand juries and all persons in active concert or participation with any of them from investigating, indicting or prosecuting the plaintiff," Miranda said.

The office of Senate Sergeant-at-Arms William Pickle (search) referred the investigation to the Justice Department after Democratic Sens. Dick Durbin of Illinois and Edward Kennedy of Massachusetts protested what they said was the theft of memos from their servers.

The memos, concerning political strategy on blocking confirmation of several of President Bush's judicial nominations, were obtained and reported by The Wall Street Journal and The Washington Times.

Conservatives have talked up the memos as proof the Democrats colluded with outside liberal groups in their choices of which Bush nominees to block with filibusters.

The sergeant-at-arms referral blamed the intrusion on Miranda, who worked for Senate Majority Leader Bill Frist and Hatch on the Judiciary Committee; and on Jason Lundell, a clerk who worked on nominations for Hatch. Miranda resigned during the dispute early this year. Lundell left late last year after word of the affair first emerged.