Consumer protection minister Ilse Aigner told German news weekly 'Focus' the company must stop saving personal data about people who are not using the network.
She told the magazine's Monday edition, "It poses me a problem if Facebook's profits are partly based on breaching existing laws."
The minister added that it collects data such as phone numbers saved in its users' devices, thereby gathering personal information of people who never agreed to share it.
German data protection officials last week launched legal proceedings against Facebook for illegally accessing and saving personal data of people who don't use the site.