Facebook has stopped using data from UK WhatsApp users after a probe into its information sharing processes from the UK's Information Commissioner's Office (ICO).
Elizabeth Denham, the information commissioner, outlined the reasons for the investigation on the ICO website.
"I had concerns that consumers weren't being properly protected, and it's fair to say the inquiries my team have made haven't changed that view," she said.
"I don't think users have been given enough information about what Facebook plans to do with their information, and I don't think WhatsApp has got valid consent from users to share the information.
"I also believe users should be given ongoing control over how their information is used, not just a 30-day window."
Denham announced her intention to look into data sharing between Facebook and WhatsApp at the end of September.
She added that Facebook has been asked to sign an 'undertaking', which basically amounts to an agreement stating that the company will better inform its users in the future.
"We have now asked Facebook and WhatsApp to sign an undertaking committing to better explaining to customers how their data will be used, and to giving users ongoing control over that information," said Denham.
"We also want individuals to have the opportunity to be given an unambiguous choice before Facebook starts using that information, and to be given the opportunity to change that decision at any point in the future.
"We think consumers deserve a greater level of information and protection, but so far Facebook and WhatsApp haven't agreed. If Facebook starts using the data without valid consent, it may face enforcement action from my office."
Denham concluded by warning that the large digital footprint internet users leave behind creates a rich seam of valuable data for companies to exploit.
"We all rely on digital services for important parts of our lives, whether it's keeping in touch with loved ones or doing our weekly shop. But our digital comings and goings create rich portraits of our lives, and vague terms of service when we sign up aren't giving us the protection we need," she said.
"It's a particular concern when company mergers mean that vast amounts of customers' personal data become an asset to be bought and sold.
"We're seeing situations where companies are being bought primarily for this data, and when it is combined with information the purchasing company already holds, there's a danger that consumers will have little control as datasets are matched and intrusive details revealed."
Facebook recently announced plans to take on the corporate collaboration market with the formal launch of Workplace by Facebook.
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