The EU has told Meta that it must allow AI chatbots operated by rival firms to use WhatsApp for free.

The European Commission said the firm would need to maintain that access while it concluded an antitrust investigation into the tech giant's decision to bar AI providers, other than Meta AI, from accessing the messaging platform.

It said the intervention was needed to prevent "serious and irreparable harm to competition in this growing market by Meta's conduct", which it said appeared to infringe EU competition rules.

Meta has reacted angrily, accusing the Commission of "regulatory overreach." It says it will appeal.

The EU said it began its investigation in December 2025 after Meta banned third-party general-purpose AI assistants from the WhatsApp for Business API.

It said that it appeared to be an abuse of Meta's dominant position in European markets.

So, as an interim measure, as its investigation continues, it has given Meta five working days to reinstate access for third-party general-purpose AI assistants to the WhatsApp for Business API under the same terms and conditions that were in place previously.

"In rapidly evolving markets, competition can be lost long before a final decision is adopted", said Teresa Ribera, the Commission's executive vice-president for clean, just and competitive transition.

"This is why these interim measures will remain in place for the duration of the investigation."

She added the decision "preserved choice for citizens across Europe on the AI assistants they want to use with WhatsApp, without that decision being made for them."

The Commission said if Meta failed to comply with its interim decision, it could be fined up to 10% up of its total turnover.

But Meta said the decision opened the door for highly valuable AI companies to access WhatsApp without paying.

"The European Commission has decided that OpenAI and some of the largest companies in the world can use the paid-for WhatsApp Business product for free", it said in a statement.

"This is regulatory overreach subsidised by the many European companies that pay. We will appeal."

The row is just the latest example of the strained relations between European regulators and US big tech firms.

Last year, Meta warned of a "worse experience" for European users because of EU regulations.

That followed a fine imposed on Meta the previous week - just one of many fines handed out by the EU, which insists it is acting in the interests of consumers in the face of tech firms seeking to take advantage of their market dominance.

The row has also turned political, with the Trump administration claiming the EU - and other jurisdictions - are unfairly targeting American tech firms.