San Francisco, Jun 19 (IANS): The fee that Apple charges developers for doing business on App Store has been likened to "highway robbery" by Congressman David Cicilline who is also the chair of US House Of Representatives antitrust committee which is probing if technology giants are harming competition in the digital marketplace, The Verge reported.

Apple has faced criticism in several markets including in Europe for the App Store fees, with the European Commission this week opening formal antitrust investigations to assess whether Apple's rules for app developers on the distribution of apps via the App Store violate EU competition rules.

The investigations concern in particular the mandatory use of Apple's own proprietary in-app purchase system and restrictions on the ability of developers to inform iPhone and iPad users of alternative cheaper purchasing possibilities outside of apps.

In the US, similar concerns were raised again after its decision to reject future updates for the iOS app of new email service Hey.

Hey is Basecamp's new $99-a-year premium email service. The controversy hit a new high after Hey did not offer a way to sign up and pay in the app itself in order to avoid paying Apple a 30 percent cut of the fee.

"Because of the market power that Apple has, it is charging exorbitant rents -- highway robbery, basically -- bullying people to pay 30 percent or denying access to their market," Cicilline told The Verge in an interview published on Thursday.

Cicilline said that hearing with the chief executives of four major technology platforms – Facebook, Apple, Google and Amazon -- could happen sometime in July.