Facebook has been ordered by a German privacy regulator to stop collecting and storing the data of German users of its messaging app WhatsApp.

The Hamburg Commissioner for Data Protection and Freedom of Information said that the social network had not obtained effective approval from WhatsApp’s 35 million German users.

Facebook bought WhatsApp for $19bn (£14.6bn) in 2014 as a way to reach out to a younger audience.

It is to appeal against the order.

“We will work with the Hamburg DPA in an effort to address their questions and resolve any concerns,” it said in a statement.

The data watchdog said that Facebook and WhatsApp were independent companies and should process their users’ data as such.

“After the acquisition of WhatsApp by Facebook two years ago, both parties have publicly assured [users] that data will not be shared between them,” said commissioner Johannes Caspar in a statement.

WhatsApp caused controversy in August when it announced that it was changing its privacy policy to allow its data to be shared with its parent company.

It said that better co-ordination with Facebook would help it to fight spam as well as allowing Facebook to offer “better friends suggestions and show you more relevant ads if you have an account with them”.

It will share phone numbers and the details of the last time that users signed on to WhatsApp.

EU and US regulators reacted with caution, saying that the update needed to be investigated. The UK’s Information Commissioner is also looking into the changes.