Facebook messaging service Whatsapp was given a one month ultimatum by the CNIL.
The CNIL, France's data protection authority, ordered Whatsapp to stop sharing user data with Facebook without getting the necessary permission.
The CNIL gave a warning to the messaging service by delivering a formal notice, criticising them for their lack of cooperation.
A statement from CNIL website this week said they had decided to make this formal notice public in order to ensure the highest level of transparency on the massive data transfer from WhatsApp to Facebook and to "alert to the need for individuals concerned to keep their data under control."
Facebook faces regulatory obstacles throughout Europe over a variety of issues. German antitrust officials could release findings in a matter of days into whether Whatsapp misuses its dominant position when users sign agreements that lets the company collect big amounts of information.
The President of Bundeskartellamt, Andreas Mundt, said that the developments would be ready buy the end of 2017.
Neither Whatsapp or Facebook replied to emails seeking comment right away.
The combining of Whatsapp information with Facebook was the first step taken by Facebook last year to monetise the social media platform since Facebook CEO Mark Zuckerberg purchased the company for $22 billion in 2014.
The transfer of information from Whatsapp to Facebook happen in part with the permission of the users, nor the legitimate interest of Whatsapp said the CNIL.
CNIL has rejected assertions from Whatsapp that they are only subject only to the law of the United States, saying that it becomes the authority in charge the moment any company is processing data in France.
The French regulator said in a statement on Monday that the formal notice was not a sanction but Whatsapp are the risk of fines alter on if they fail to abide by it.