Britain's data protection watchdog says it has fined Facebook 500,000 pounds (645,000 dollars) for "serious breaches of data protection law" in connection with the Cambridge Analytica scandal.

The Information Commissioner's Office said the fine followed an investigation that found "Facebook processed the personal information of users unfairly by allowing application developers access to their information without sufficiently clear and informed consent."

It said Facebook also "failed to keep the personal information secure," leading to one developer harvesting data that was partially shared with firms including SCL Group, Cambridge Analytica's parent company.

The watchdog said it applied the maximum fine possible "after considering representations" from Facebook.