The EU has threatened to take action against the social media company Meta, arguing it has blocked rival chatbots from using its WhatsApp messaging platform.

The European Commission said on Monday that WhatsApp Business – which is designed to be used by businesses to interact with customers – appears to be in breach of EU antitrust rules.

An upgrade to the messaging platform last October means the only AI assistant available to use on WhatsApp is Meta AI, the agent developed by the US tech group, which also owns Facebook and Instagram.

The European Commission said Meta was the dominant player for messaging in the EU market and was “abusing” this position by “refusing access to WhatsApp to other businesses”.

That position may cause “serious and irreparable harm on the market”, the commission added. It said it “considers that WhatsApp is an important entry point” for AI chatbots such as OpenAI’s ChatGPT, to “reach consumers”.

The warning comes amid heightened tension between European authorities and Donald Trump’s administration over the regulation of US tech companies. Brussels is reportedly preparing to intensify enforcement of its key anti-competition rules and the Trump administration has said this is “discriminatory” against US companies.

“It is very obvious that we need to defend, to implement and to enforce our rules, to defend our market, a well-functioning market,” the EU competition commissioner, Teresa Ribera, told Bloomberg.

In December the US imposed sanctions on the former European Commissioner Thierry Breton as well as four other European “activists”, accusing them of censorship and “suppress[ing] American viewpoints”. The move was widely seen as an escalation in response to European regulation of US tech platforms.

Breton is challenging the sanctions, and the commission has announced it will back him.

Asked about a potential US response to the EU’s measures against WhatsApp, Ribera said: “I don’t know how it may be read by any government, but my sense is that this is not connected to politics, but connected to well-functioning markets.”

A Meta spokesperson said: “The facts are that there is no reason for the EU to intervene in the WhatsApp Business API. There are many AI options and people can use them from app stores, operating systems, devices, websites, and industry partnerships.

“The commission’s logic incorrectly assumes the WhatsApp Business API is a key distribution channel for these chatbots.”

Last month, Brazilian authorities brought a similar case against WhatsApp Business, saying that there were “potential anti-competitive practices” in the new terms, Reuters reported.

That case was suspended, with Meta saying its claims were “fundamentally wrong,” and that the “emergence of AI chatbots on the WhatsApp Business Platform overloads our systems, which were not designed for this type of support”.