Apple conspired with publishers to fix the price of electronic books, a US judge has ruled.
Manhattan Judge Denise Cote said the iPad maker "conspired to restrain trade".
But the firm's spokesman, Tom Neumayr, said Apple would appeal against the ruling and fight "false allegations".
The BBC reports that five publishers that were originally named as defendants alongside Apple have already reached settlements, including Penguin.
The judge ordered a new hearing to determine damages to be imposed on Apple.
The US Department of Justice said the conspiracy was designed to challenge online retailer Amazon's dominance of the fast-growing e-books market.
Penguin settled its case for $US75 million. Hachette, HarperCollins and Simon & Schuster created a $US69m fund for refunds to consumers, while Macmillan settled for $US26m.
Judge Cote said: "The plaintiffs have shown that the publisher defendants conspired with each other to eliminate retail price competition in order to raise e-book prices, and that Apple played a central role in facilitating and executing that conspiracy.
"Without Apple's orchestration of this conspiracy, it would not have succeeded as it did in the spring of 2010," she said.