The suit, filed in U.S. District Court Tuesday by the American Civil Liberties Union and the Council on American-Islamic Relations, charges the bureau hired an informant to spy on worshipers at several mosques to root out potential terrorists, the Los Angeles Times reported.
The suit names seven FBI employees, including Director Robert Mueller, accusing them of paying resident Craig Monteilh to infiltrate mosques and record conversations.
The 64-page document seeks class-action status, unspecified damages and a court order instructing the FBI to destroy or return the information Monteilh collected, The Washington Post reported.
"The FBI should be spending its time and resources investigating actual threats, not spying on every American who happens to worship at a mosque," said Peter Bibring, a staff attorney for the ACLU of Southern California.
The FBI has declined to comment on the suit.