Citing national security, Ashcroft recently classified documents related to the case of Sibel Edmonds, a former linguist at the FBI. The lawsuit charged that reclassifying materials that had previously been in the public domain is illegal and unconstitutional.
The suit was filed in federal court by the Washington-based Project on Government Oversight, a nonprofit group that has been following the case.
In 2002, Edmonds told her bosses of her concerns about shoddy translations and suggested one interpreter with a relative who works at a foreign embassy may have compromised national security. She was fired soon after. The bureau cited performance issues as reasons for the dismissal.
Ashcroft told Senate Judiciary Committee members at a hearing earlier this month that he took responsibility for the decision to classify the Edmonds' information.
"The national interests of the United States would be seriously impaired if information provided in one briefing to the Congress were to be made generally available," he said.
The lawsuit said that Edmonds' case was discussed by the FBI during unclassified Senate Judiciary Committee briefings in 2002. It said letters urging the FBI to investigate her claims were posted on the Web sites of Sens. Patrick Leahy, D-Vt., and Charles Grassley, R-Iowa.
Those letters have since been removed from the Web sites.
"This is an extraordinary and dangerous abuse of power by Ashcroft to improperly use the classification system to hide information that the Justice Department finds embarrassing," said Danielle Brian, executive director of the project.
The group has been investigating Edmonds' allegations and wants to post its findings on its Web site, but is barred from doing so now because of the reclassification, Brian said.
Justice Department spokesman Charles Miller declined to comment on the lawsuit.