The US Department of Justice has filed an antitrust lawsuit against Apple and five publishing houses - Hachette, HarperCollins, Macmillan, Penguin and Simon & Schuster - in New York district court, alleging they conspired to fix the pricing of e books.

Speaking at a news conference U.S. Attorney General Eric Holder said that executives at the highest levels of Apple and the publishers worked together to eliminate competition among sellers of e-books.

The Justice Department accused Apple of colluding with five publishers, as the Silicon Valley giant was launching its iPad in early 2010 and was seeking to break up Amazon's low-cost dominance in the digital book market.

Sources earlier told Reuters that Apple and MacMillan were the only two named in the lawsuit who didn't engage with the DOJ once it warned all six involved that the lawsuit was on its way. Both deny claims they colluded to fix e-book prices.

All parties involved, including the Justice Department's antitrust division, have refused to speak publically on the matter. The US government is seeking a settlement that would let Amazon and other retailers return to a wholesale model, where retailers decide what to charge customers, sources have said.