Apple is facing yet another challenge to its App Store, with a new class-action lawsuit in the UK that seeks $1 billion in damages over antitrust accusations.

According to TechCrunch, Sean Ennis, a professor of competition policy at the University of East Anglia, is bringing the suit against Apple. Ennis has previously served at the OECD, DOJ, and EU Commission.

The lawsuit is opt-out, meaning more than 1,500 UK app developers are automatically represented. The suit alleges that Apple’s 30% cut of purchases is “anticompetitive.”

“I have been studying competition questions for decades — and digital competition for quite a long time. I’ve written about it in technical economic papers but also in less technical work. And I’m really convinced that the type of behaviour we’re talking about in this case is deeply problematic. So I was interested in taking a role to help get some redress for those who I feel have been harmed by the behaviour,” he told TechCrunch.

Ennis also takes issue with the extra fees Apple collects, including the $99 per year developer fee, as well as the various costs developers incur promoting their apps in the App Store.

“Another element that is critical is that even if the fee was zero, you would still have the same App Store because Apple could not sell a single device without valuable apps such as Tinder, Spotify, Netflix, news apps, game apps and the like,” he told the outlet. “It’s only because they have created a monopoly of distribution for themselves that they’re able to collect this extraordinary commission.”

If the lawsuit is successful, it could represent substantial payouts for developers, well into the millions in some cases.