WhatsApp has been warned by the pan-European privacy watchdogs over its sharing of information with Facebook and asked to pause the transfer of personal data.

The gathered European Union data protection authorities, collectively known as the Article 29 Working Party, said they had serious concerns over WhatsApp’s recent privacy policy change and the sharing of user phone numbers with its parent company Facebook.

Article 29 said that it had “requested WhatsApp to communicate all relevant information to the Working Party as soon as possible and urged the company to pause the sharing of users’ data until the appropriate legal protections could be assured” in a letter sent to the messaging service.

A WhatsApp spokesperson said: “We’ve had constructive conversations, including before our update, and we remain committed to respecting applicable law.”

The data protection authorities also wrote to Yahoo over its massive data breach that exposed the email credentials of 500 million users in 2014, as well as its scanning of customers’ incoming emails for specific information provided by US intelligence officials.

Article 29 requested information on all aspects of the data breach, that Yahoo must notify users its “adverse effects” and commanded it to cooperate with all “upcoming national data protection authorities’ enquiries and/or investigations”.

In a statement regarding the company’s email scanning for US intelligence agencies Article 29 said: “Yahoo was invited to provide information on the legal basis and the compatibility with EU law of any such activity.”

The Working Party will discuss the Yahoo and WhatsApp privacy cases in November.

The letters come as European nations express concern over WhatsApp’s changes and Yahoo’s mishandling of its hack and the revelations over US intelligence operations.

Germany recently ordered Facebook to stop collecting WhatsApp user data, and to delete any that it had already acquired, while the United Nations warned that Yahoo’s actions raised serious human rights concerns.