Google issues warning to location-sharing apps
Google has warned app developers that they need to be clear with users about the information they share with Huq, a British firm that sells location data.
Google has said apps which fail to comply with their data policy face being banned from its Play store.
It comes after Huq admitted to the BBC that at least two app partners had not sought the correct user permissions.
Huq said the firm took data protection "very seriously" and it believed all partners were now in compliance.
App partnerships and the sharing of data with third-parties is under increased scrutiny from regulators and policy-makers around the world.
Huq partners with a range of apps, including a Muslim prayer app, a flight-tracking app and a weather app.
App developers embed some lines of code supplied by Huq which feed back location data - which Huq then collates. This information is then sold on to clients, including a range of UK councils.
But an article by Vice in October raised doubts over whether people were aware that information was being shared when they used these apps.
Huq then admitted to the BBC that at least two apps shared information with the firm, without seeking proper permission from users.
In October, Google introduced a new user data policy informing apps that they must be clear about how any data they collect is used.
Google said: "As part of our investigation, we have sent a warning to all app developers that we determined were in violation of Google Play policies."
But it declined to say how many app developers had received the warning.
Huq's chief executive Conrad Poulson said: "We continue to take the matter of data protection and consent very seriously and actively support any initiative designed to make improvements in this regard.
"It is extremely important to us that we continue to work alongside our partners to help ensure privacy best practices are implemented and maintained."
The BBC has also asked Apple for comment.