BERLIN- The German Federal Court on Thursday referred a lawsuit filed by a consumer protection watchdog alleging privacy violations by Facebook to the Court of Justice of the European Union to seek clarification on the applicable law.

The long-running case, brought by the Federation of German Consumer Organisations (vzbv), alleged that the social network had allowed operators of online games to improperly collect the personal data of people who played them.

Facebook declined to comment on the court statement pending the release of a full written judgment.

A lower court ruled in favour of the vzbv and Facebook appealed the decision.

In its written ruling, the Federal Court said it was suspending the case to seek advice from the European Court as interpretations of the applicable law varied.

"This question is disputed both in court judgments and in the literature," the court, based in Karlsruhe, said in a statement.

At issue were online games offered on Facebook's App Center back in 2012 in which, by playing them, a user automatically agreed to share personal data including their email address.

At the end of the game, users would see a message saying that the app could post their status, photos and other information.

Such games - including quizzes - were widely used at the time to harvest data on users of Facebook. The company subsequently overhauled its privacy settings, although they have continued to be a source of controversy.

The European Union's two-year-old privacy rulebook, the General Data Protection Regulation (GDPR), stipulates that any requests to collect personal data should be subject to clear, informed consent.

However it is not clear, according to the Karlsruhe court, whether organisations that can bring litigation under national law have the necessary standing to press their case under the GDPR. It is seeking clarification on this matter of principle.

(Reporting by Douglas Busvine; editing by Jason Neely) ((douglas.busvine@tr.com; +49 30 2888 5084; Reuters Messaging: douglas.busvine.thomsonreuters.com@reuters.net))