WhatsApp asked its users to agree to its new updated terms, which would allow the service to share users' data with Facebook and facilitate e-commerce.
The terms include facilitating e-commerce through WhatsApp, as Facebook tries to monetize the messaging service.
The new terms would allow users of WhatsApp Business to use the updated functions in the EU and the UK, a company's spokesperson told news agency AFP.
WhatsApp asked its users to agree to the new terms and conditions, or no longer have access to the app.
Privacy advocates sharply criticized the update, with some warning that the new terms were not legal.
Arthur Messaud, a lawyer for La Quadrature du net, an association that defends internet users, told news agency AFP that the update was unlawfully forcing users to agree to the breach of their data if they wanted to keep using the messaging service.
"If the only way to refuse (the modification) is to stop using WhatsApp, the the consent is forced as the use of personal data is illegal," he said.
The update has sparked anger among some WhatsApp users, who are considering switching to other instant messaging services. Tesla chief and billionaire Elon Musk took to Twitter to call for people to switch to apps like Signal.
Within hours of the WhatsApp announcement, messaging app Signal said it was dealing with an overload of new users.
Signal was developed by data privacy activists to implement a sealed sender policy, concealing the messages metadata, which could typically reveal the sender, receiver and timing of messages.
WhatsApp was once considered a safe instant messaging software, thanks to its end-to-end encryption.
European Union politicians used the app during Brexit negotiations, giving rise to the term "WhatsApp diplomacy." The European Commission later changed course, urging its employees to switch to Signal, citing privacy concerns.
In May 2020, Germany's data privacy commissioner Ulrich Kelber advised against using WhatsApp in federal ministries and institutions, urging government bodies to respect data protection.
WhatsApp's parent company Facebook has been on a collision course with regulators in the United States and the EU for years, with the situation coming to a head at the end of 2020.
In December, the US Federal Trade Commission and 48 states in December filed a lawsuit against Facebook for violating competition laws, accusing the social medium of market monopoly.
The EU fined also Facebook €110 million (then $120 million) for misleading its users about the company's power to link accounts between its other services following its controversial takeover of WhatsApp.
Facebook took over WhatsApp in 2014, two years after buying the photo service Instagram.