Apple is facing mounting pressure over how it runs its app store ahead of its major global developers’ conference, which starts on Monday.
The firm has been accused of creating “hostile” policies within its fee structure, and is dealing with two EU competition probes announced this week.
But it is also embroiled in a row with some of its own developers.
That has now widened into a debate involving politicians and other major technology firms.
Apple’s Worldwide Developers Conference often features new product announcements but is mainly an event for software developers working on Apple’s platforms – some of whom are now voicing discontent about its pricing.
The argument was ignited in part by an email app called Hey, created by developer David Heinemeier Hansson. It had an update rejected by the Apple app store early this week because it does not allow in-app purchases – from which Apple takes a 30% cut.