Facebook is facing legal action in Germany over its controversial facial-recognition feature.

The state data protection authority in Hamburg is preparing to sue the social-networking giant over the feature, which automatically recognizes and tags photos in Facebook users' networks, according to a report in Deutsche Welle.

"This requires storing a comprehensive database of the biometric features of all users," the organization reportedly wrote in a German-language statement published on its Web site. "Facebook has introduced this feature in Europe, without informing the user and without obtaining the required consent. Unequivocal consent of the parties is required by both European and national data protection law."

The organization said it has had conversations with Facebook in which the company promised it would inform users of the feature, adding that "further negotiations are pointless."

Facebook responded by saying a lawsuit was "completely unnecessary."

"The Tag Suggestions feature on Facebook is fully compliant with EU data protection laws," Facebook representative Andrew Noyes said in a statement. "On top of that, we have given comprehensive notice and education to our users about Tag Suggestions and we provide very simple tools for people to opt out if they do not want to use this feature. We have considered carefully different options for making people even more aware of our privacy policies and are disappointed that the Hamburg DPA has not accepted these."

The feature was quietly rolled out in June and immediately attracted the regulatory attention of the European Union, which announced it would study the feature for possible rule violations. Authorities in the U.K. and Ireland have also said they are reviewing the photo-tagging feature.

U.S. lawmakers criticized the company for making the requiring users to opt out of the feature rather than opt in. "Requiring users to disable this feature after they've already been included by Facebook is no substitute for an opt-in process," Rep. Edward J. Markey (D-Mass.), co-chairman of the Congressional Privacy Caucus, said in a statement in June.

Even though Facebook allows users who don't want to be identified by the feature to disable it, the company conceded at the time that it could have done a better job explaining how the feature works.

"We should have been more clear with people during the roll-out process when this became available to them," the company said in a statement in June.