Lawyers for the Facebook owner served notice of an appeal against the decision to place WhatsApp and Instagram, both owned by Meta, in a category carrying additional regulatory duties.

Those duties include greater transparency, increased user controls, measures to protect users from fraudulent advertising and enhanced recording of illegal content.

Meta has already challenged Ofcom in London over the fees it is required to pay to fund the regulator’s online safety work, arguing in May that the methodology was flawed because it was based on global revenue.

The Online Safety Act allows breaches to be punished with fines of up to 10 per cent of qualifying worldwide revenue (QWR) or £18 million, whichever is higher.

TikTok and X have also taken legal action over the amount of information they must provide to Ofcom to enable it to monitor their services.

Oliver Griffiths, Ofcom’s group director for online safety, told a House of Lords committee last week that the regulator was “operating in a highly litigious environment”.

“We absolutely are looking to drive change in the best way we can,” Oliver Griffiths, the Ofcom group director for online safety, told peers. “We have all come to work to make this happen, but, if we run unnecessary risks, we are going to get absolutely clobbered legally by deep-pocketed individuals and firms.”

A Meta spokesperson said: “Like many others in the industry, including TikTok, Roblox, X and Quora, we are challenging specific aspects of implementation.

“These are not challenges to the law itself, but how Ofcom has interpreted it. This is a normal feature of any new regulatory regime being bedded in and ensures questions of process, scope and implementation get settled so the law is applied proportionately, accurately and consistently.”