Apple has rebuffed allegations from the Department of Justice (DoJ) that it and five major publishers colluded to fix the price of e-books, calling the claims "simply not true".
In a statement the firm dismissed the claims and said that its iBookstore service had helped create a more dynamic market for e-books and followed the same pricing set-up as its App Store.
"The launch of the iBookstore in 2010 fostered innovation and competition, breaking Amazon's monopolistic grip on the publishing industry," it said.
"Just as we've allowed developers to set prices on the App Store, publishers set prices on the iBookstore."
The DoJ issued legal proceedings against Apple and five large book publishers on Wednesday over claims they conspired to raise e-book prices.
US attorney general Eric Holder claimed the firm's collusion had directly impacted consumers.
"As a result of this alleged conspiracy, we believe that consumers paid millions of dollars more for some of the most popular titles," he said.
Since the case on Wednesday, Australian regulators have also begun looking into whether similar practices occurred in their country, while European regulators began their investigation in December.
The issue tops a tough weeks for Apple in which it has also had to deal with the Flashback malware on its Mac OS X systems, issuing a second fix on Thursday to try and combat its spread.
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