Activity tracker shares users' information with its parent, despite earlier promise not to 'commingle' data between the companies

Eleven days after being purchased by Facebook, the activity tracking app Moves has changed its privacy policy to allow it to share user data with its parent company.

The new version of the app's privacy policy allows it to "share information, including personally identifying information, with our affiliates (companies that are part of our corporate groups of companies, including but not limited to Facebook)".

Moves uses motion sensors inside Apple and Android phones, as well as GPS information, to track a user's location and activity throughout the day. Not only does its information include someone's whereabouts, down to which building they were in when they started using the service, it even knows if they travelled between locations on foot, bike or bus.

On the day of its acquisition, the company promised users that "the Moves experience will continue to operate as a standalone app, and there are no plans to change that or commingle data with Facebook". A Facebook spokeswoman told the Wall Street Journal that that remained the case, but that the companies would share data.

The Guardian has asked Facebook to clarify the difference between "share" and "commingle", but has received no reply at press time.

Under its old privacy policy, Moves was committed to notifying users of any change to the policy "through the service, by email, via our Twitter account or otherwise". While a banner at the top of the Moves app does warn users of changes, no emails or tweets have been sent out.

Previously, the Moves privacy policy allowed it to disclose an individual user's data to third parties if "our business or assets, or parts of them, are acquired by a third party".

The change comes after Facebook's F8 developer conference, where the company promoted a new, privacy-friendly version of itself. Users will now be able to log in to apps anonymously, letting them try them out before they need to provide them with personal information.