Consumer privacy group Electronic Privacy Information Center has filed a formal complaint with the US Federal Trade Commission claiming Facebook broke the law when it conducted a study on the emotions of its users without their knowledge or consent, USA today reports.

The privacy watchdog alleges Facebook deceived users by secretly conducting a psychological experiment to determine if positive or negative updates in its users’ news feeds effect their emotions.

It claims Facebook along with researchers from Cornell University and the University of California, “failed to follow standard ethical protocols for human subject research”.

“At the time of the experiment, Facebook did not state in the Data Use Policy that user data would be used for research purposes,” says the center.

“Facebook also failed to inform users that their personal information would be shared with researchers.”

“Moreover, at the time of the experiment, Facebook was subject to a consent order with the Federal Trade Commission which required the company to obtain users’ affirmative express consent prior to sharing user information with third parties.”