Facebook faces legal action from a German data protection watchdog over its face recognition feature, which automatically recognises and tags photos posted on the social network.
German news site Deutsche Welle reports that Hamburg's state data protection authority set out its objections to the features in a German-language statement on its web site
"This requires storing a comprehensive database of the biometric features of all users," the organisation wrote. "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."
Facebook quietly rolled out face recognition in June this year, amid criticism that users were required to specifically opt out of the feature.
Hamburg's data protection authority says that despite a number of assurances from the social network that it would provide better information to users in future, "further negotiations are pointless" - and the organisation intends to sue.
"We believe that any legal action is completely unnecessary," Facebook spokesperson Andrew Noyes responded in a statement. "The tag suggest feature on Facebook is fully compliant with EU data protection laws.
"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."