A watchdog group sued the State Department and the National Archives and Records Administration Wednesday in an effort to force a probe of Hillary Clinton's private email server.

Cause of Action, a nonpartisan nonprofit, said the case is the "first federal action filed to mandate retrieval of former Secretary of State Hillary Clinton's records" from her private email server.

The group cited the Federal Records Act, which bars officials from removing records of any form from government agencies, in its push for Secretary of State John Kerry and Archivist David Ferriero to pursue Clinton's undisclosed emails through legal action.

"As Clinton knew or should have known, the Federal Records Act did not authorize her to set up her own record-keeping system or to maintain emails on a personal server or use a private email account without ensuring that the emails were concurrently archived in the State Department's official record-keeping system," Cause of Action argued in court filings.

Clinton claimed in an interview Tuesday that her use of a private system to shield her communications from the agency didn't violate any laws.

Dan Epstein, executive director of Cause of Action, said the fact that State and National Archives officials are brushing off revelations that Clinton withheld government emails from the public amounts to "brazen neglect at best and cover-up of illegal activity at worst."

"This case is about no government official being above the law and the duty of Secretary Kerry and Archivist Ferriero to fulfill their statutory obligations to hold former Secretary of State Hillary Clinton accountable for misusing taxpayer-funded federal property," Epstein said.

Among the documents cited in the federal court case Wednesday was a letter from David Kendall, Clinton's attorney, in which he claimed an email address, hrod17@clintonemail.com, was "not an address that existed during Secretary Clinton's tenure."

That email account has surfaced repeatedly in the handful of email exchanges that have been made public this year.

Kendall's letter also revealed Rep. Trey Gowdy, chairman of the House Select Committee on Benghazi, sent a letter to Clinton March 19 asking that she turn over her private server to a neutral third party for review, a request Kendall denied.

Calls to retrieve Clinton's private server have grown in recent weeks following the discovery that she withheld work-related emails from the State Department when she submitted her records at the end of last year.