Apple has said that it hasn't changed its App Store guidelines and rejected criticism from Sony over in-app purchases.

Sony lashed out at Apple after an app it created, which would have allowed users to buy and read books from the Sony Reader Store, was rejected by Apple after going through the App Store review process.

Sony's Steve Haber, told the New York Times that Apple had told Sony that all in-app purchases had to be made through Apple or the apps wouldn't be allowed into the App Store.

Haber, president of Sony's digital reading division, told the New York Times: "We always wanted to bring the content to as many devices as possible, not one device to one store," adding that having to go through Apple to sell content within Sony apps was "opposite of what we wanted to bring to the market".

But Apple has since told the All Things Digital website that it had not changed its guidelines.

"We have not changed our developer terms or guidelines. We are now requiring that if an app offers customers the ability to purchase books outside of the app, that the same option is also available to customers from within the app with in-app purchase," an Apple spokeswoman told the site.

So Apple merely wants Sony to provide an app that uses Apple's In App Purchase API, though is willing to let that function sit alongside a content-purchasing system that doesn't go through iTunes at all.

For example, Amazon's Kindle app offers access to content that had been purchased by the app's owner, though to actually buy content, the Kindle app opens the Safari browser on an iOS device where the purchase can be made, bypassing iTunes.

As the report notes, this seems to suggest that Amazon will be required to offer an in-app purchasing mechanism based on Apple's API or face removal from the App Store.

Apple also looks set to answer further questions about App Store purchases on Wednesday, this time relating to how subscription-based apps such as News Corp's The Daily will work.

The Daily is holding a launch event in New York's Guggenheim Museum on Wednesday.