Germany's data protection agency has accused the California-based social network further, by stating it believes Facebook may be tracking the Internet activity of users -- even after they cancel their accounts.
This comes as European Union regulators adds further pressure to Facebook, amid a series of privacy related controversies.
The agency's head, Johannes Caspar, said on its website: "Arguments that all users have to remain recognisable after they leave Facebook to guarantee the service’s security can’t stand up", adding: "The probe raises the suspicion that Facebook is creating user tracking profiles", accusations which would be illegal under European law if users' were not informed.
While Facebook gave detailed explanations of how it used cookies as part of the site's experience, the company "did not justify its practices".
Facebook continues to deny these claims, with the company reaffirming its position, stating that it "does not track users across the Web", but that cookies may be used to personalise content on other websites.
The social networking giant, after at first denying that cookies could track users outside of Facebook, issued a fix last month, adding that the issue was "limited in scope".
Ireland's data protection commissioner is also pushing ahead with a privacy audit of the company's practices, amid allegations that data is held on users even after content is removed, or a user's profile is deleted.
Though Facebook has its international headquarters in Dublin, the results of the privacy audit could affect all 800 million users worldwide of the social network, including those based in the United States and Canada.
Norway's data protection agency is also investigating Facebook over privacy practices, adding to further pressure on the social networking giant.