Facebook already has been buried in an avalanche of other lawsuits filed in federal and state courts, as well as regulatory investigations in both USA and Europe into whether the company has violated laws by repeatedly allowing unauthorized access to the personal information of the almost 2.3 billion people on its private network.
The scandal turned the spotlight on Facebook and prompted mass criticism of how the company deals with user data and other privacy issues.
The action appears to be the first from a USA prosecutor since revelations about were first reported in March.
Privacy settings on Facebook to control what friends on the network could see and what data could be accessed by apps were also deceiving, Ms Racine said.
Facebook has repeatedly assured lawmakers, regulators and the media that it is battening down its hatches in an effort to do a better job preventing unauthorized access to the pictures, thoughts and other personal information that its almost 2.3 billion users typically intend to share only with friends and family.
The lawsuit alleges that Facebook told users that it would protect their personal information, but allowed the app developer to collect and sell the data of users who hadn't downloaded or used the app.
District of Columbia Attorney General Karl Racine is suing Facebook.
The social network has admitted that up to 87 million users may have had their data hijacked by Cambridge Analytica, which shut down weeks after the news emerged on its handling of private user information.
Facebook is being sued by the DC attorney general over allegations it failed to safeguard the personal data of its users. 'We hope this lawsuit will ensure Facebook takes better care with its data'.
The lawsuit accuses Facebook of violating DC's consumer protection law.
That bombshell triggered congressional hearings and changes in what sorts of data Facebook lets outside developers access.
Facebook has already produced "reams of documents" in response to the attorney general's investigation, officials said. A copy of the full complaint against Facebook can be viewed here. In addition to threatening Facebook's reputation, the suit could potentially cost the company billions.
Revelations about Facebook's response to manipulation of the social network before and after the 2016 US presidential election, and shifting accounts about breaches of users' privacy, have battered the company's reputation and fueled frustration on Capitol Hill.