Epic Games founder Tim Sweeney has branded Apple and Google "exploitative" for imposing a 30 percent store fee on their respective mobile platforms.

It's hardy surprising to see Sweeney slam the once standard 30 percent store fee, given his own marketplace the Epic Games Store only takes a 12 percent cut from developers. 

The Epic chief exec has previously called for a "more general change to smartphone industry practices" that would make platforms like the App Store and Google Play Store more open to developers, allowing them to do things like use third-party payment services for in-app purchases.

"This is a critical consideration in these 30 percent store fees," wrote Sweeney on Twitter. "They come off the top, before funding any developer costs. As a result, Apple and Google make more profit from most developers' games than the developers themselves. That is terribly unfair and exploitative.

"It pains me to complain about Apple in this way. Apple is one of the greatest companies that has ever existed, perhaps the greatest. But they're fundamentally wrong in blocking competition and choice on devices they make, and that holds up entire fields of technological progress."

When asked how he would tweak those mobile platforms, Sweeney again suggested the best solution would be to open them up to competing payment options and stores. 

"The best solution is for Apple and Google to truly open these platforms up to competing payment services and to competing stores. Competition will ensure that every service provider can compete on fees, and that customers get the best prices on software."