Messaging app has one month to comply or it will face sanctions for sharing user phone numbers and usage data for ‘business intelligence’ purposes.

WhatsApp has been ordered to stop sharing user data with parent company Facebook or face sanctions.

The French data protection agency, Commission Nationale de l’Informatique et des Libertés (CNIL), said on Monday that WhatsApp did not have a legal basis to share user data under French law for “business intelligence” purposes. The messaging app must cease data sharing within a month, paying particular attention to obtaining users’ consent.

The watchdog said WhatsApp had violated its obligation to cooperate with CNIL and had not properly obtained users’ consent to begin sharing their phone numbers with Facebook.

“The only way to refuse the data transfer for ‘business intelligence’ purpose is to uninstall the application,” the CNIL said in a statement.

CNIL said that it considers the transfer of some data for security purposes to be legal, but that the sharing of non-essential information to improve the function of the app was not as users were not given the possibility to opt out.

Facebook bought WhatsApp in 2014, stating that it would begin sharing data from the messaging app to the wider social network’s ecosystem in 2016.

The move, which Facebook said was not possible at the time of acquisition of the messaging app, drew warnings from data regulators over explicit consent.

In October, European Union privacy regulators rapped WhatsApp for not resolving their concerns over the sharing of user data with Facebook a year after they first issued a warning.

The European Commission fined Facebook €110m (£94m) in May for providing incorrect and misleading information on its takeover of WhatsApp.

Only small fines can be issued by European data protection authorities currently, but from May 2018 the new EU General Data Protection Regulations will come into force, permitting fines up to 4% of global turnover, which translates as €20m.

CNIL said it had repeatedly asked WhatsApp to provide a sample of French users’ data transferred to Facebook but the company had explained it could not do so as it is located in the United States and “it considers that it is only subject to the legislation of this country”.

WhatsApp said in statement: “Privacy is incredibly important to WhatsApp. It’s why we collect very little data, and encrypt every message.

“We will continue to work with the CNIL to ensure users understand what information we collect, as well as how it’s used. And we’re committed to resolving the different, and at times conflicting, concerns we’ve heard from European Data Protection Authorities with a common EU approach before the General Data Protection Regulation comes into force in May 2018.”