The US Justice Department filed an antitrust lawsuit naming Apple and five publishing houses alleging a "conspiracy to limit" e-book price competition, court documents showed.

The suit filed in US District Court in New York said the conspiracy involved "schemes to limit Amazon's ability to discount e-books," hurting consumers.

The lawsuit comes amid probes on both sides of the Atlantic over the efforts to limit discounting on electronic books, which had been dominated by Amazon until Apple launched its iPad in 2010.

The US lawsuit said the publishers "shared a common objective with Apple to limit e-book retail price competition."

Named in the suit along with Apple were CBS Corp.'s Simon & Schuster; Hachette Book Group, part of France's Lagardere; Pearson's Penguin Group; Macmillan, a unit of Verlagsgruppe Georg von Holtzbrinck; and HarperCollins, a unit of News Corp., which owns The Wall Street Journal.

iPad ebook via Adam Radosavljevic/