Germany's data protection commissioner has told Facebook it must stop collecting information on its users from its subsidiary WhatsApp.
Johannes Caspar also told the firm to delete any data it has already received from the instant messaging service, reports Deutsche Welle.
The commissioner said Facebook had reneged on a 2014 promise to keep the data of the two services separate, a vow made when it bought WhatsApp for approximately £14.8bn.
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WhatsApp notified users of the change in policy in August, saying they would have to opt out if they were not happy with the plan.
However, Caspar said this did not go far enough and that as a separate entity, Facebook should have asked WhatsApp users for permission to collect their data. He has now ordered the social network giant to ask WhatsApp's 35 million German users exactly that.
"It has to be their decision whether they want to connect their accounts with Facebook. Facebook must ask their permission in advance [but] this did not happen," he said.
"The fact that this is now happening is not only a misleading of their users and the public, but also constitutes an infringement of national data protection law."
Caspar is the commissioner for data protection and freedom of information for Hamburg, the city where Faceboook has its German headquarters. As such, it is his responsibility to police the site's activities in Germany.
Facebook at first said it was ready to co-operate with the German authorities, saying: "Facebook complies with EU data protection law. We are open to working with the Hamburg DPA in an effort to address their questions and resolve any concerns."
However, Reuters later reported the company plans to appeal the ruling.
Italy's privacy watchdog said yesterday it was also investigating the sharing of data between Facebook and WhatsApp, adds the news agency. Deutsche Welle reports this is just the latest in a series of fights between European governments and internet giants over data protection.
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