Spotify has hit out at Apple over competitiveness, just a day after US senator Elizabeth Warren did the same.

The music streaming service accused the iPhone maker of using its App Store approval process as a weapon , after a new version of the Spotify app for Apple s iOS was rejected by the technology giant.

In a letter sent to Apple s lawyers, Spotify claims that Apple is causing grave harm to Spotify and its customers by rejecting the update because it was not set up to use Apple s payment system within the app, something Apple insists on as part of its business model rules .

Though Apple does not require subscription services to use its iTunes billing system, it does not allow them to use an alternative payment system within an app.

The letter claims that Apple demanded Spotify uses Apple s system if the streaming service wants to use the iPhone app to acquire new customers and sell subscriptions.

Spotify has taken issue with this as not only does Apple have a rival streaming service – Apple Music – but it also charges a 30% monthly fee for those who do use its billing service.

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