Epic Games CEO Tim Sweeney has publicly criticised Apple's plans to scan users' iCloud photos and messages as a way to prevent the spread of child pornography.

This initiative, Sweeney argues in an eight-tweet thread, leaves the door open for government agencies to spy on Apple users, reports AppleInsider.

"I've tried hard to see this from Apple's point of view," he writes in the initial post. "But inescapably, this is government spyware installed by Apple based on a presumption of guilt. Though Apple wrote the code, its function is to scan personal data and report it to government."

Sweeney goes on to draw a distinction between content moderation on a public forum and the scanning of private data, to point out that many Apple users were obliged to sign up for an iCloud email address under previous signup protocols, and to predict that public sentiment will be manipulated in support of the initiative.

"Liberty," he concludes, "is built on due process and limited government. The existential threat here is an unholy alliance between government [and] the monopolies who control online discourse and everyone's devices, using the guise of private corporations to circumvent constitutional protections."

The comments are prompted by an Apple plan - applying only to US owners, at least initially - to use an algorithm to compare images in iCloud Photos against known material depicting the sexual abuse of children. The search will use machine learning, but if a matching image is discovered, it will be examined by human eyes for verification.

Without wishing to imply that the Epic CEO's comments are motivated by anything other than his own ideological objections to Apple's plans, it's worth pointing out that the two companies have history. They have previously been involved in a long-running legal battle in which Epic accused Apple of exercising a monopoly via the App Store.

And Sweeney was promptly criticised for double standards, because Epic Games is 40% owned by the Chinese tech giant Tencent - a company suspected of having collaborated with the Chinese government to monitor non-Chinese users and censor content on the messaging app WeChat.

This article originally appeared on Macworld Sweden. Translation and additional reporting by David Price.