Apple has been sued by app developers who claim the company's App Store constitutes an illegal monopoly, enabling the company to charge the developers an inflated fee on app sales.

The two developers, which are seeking to launch a class action suit against the iPhone maker, say Apple exercises unfair control over how apps are downloaded on its iPhones by shutting out rivals to its App Store.

They say this unfairly forces developers to pay Apple's the 30pc fee it levies on sales of their apps, as well as stick to mandated price points that require them to sell apps at a price ending in .99.

"From the outset, Apple attained monopoly power in the US market for iOS app and in-app-product distribution services by slamming the door shut on any and all potential competitors. And it has barred the door ever since," according to the complaint filed in a court in California.

The developers, which make a baby-naming app and a basketball app, are seeking damages and an order banning Apple from anticompetitive behaviour.

The lawsuit is the latest legal challenge to the App Store, which is under growing scrutiny from regulators. Earlier this year the US Supreme Court ruled that a long-running lawsuit from Apple users, claiming the company operates the App Store as a monopoly, can go ahead.