The US government has filed a lawsuit against five publishers and the country's most valuable firm, Apple, accusing them of price fixing in the eBook market.
The US department of justice (DOJ) said the group of publishers conspired to limit competition through price fixing.
The move follows a similar probe by European anti-trust authorities announced in December to determine whether the firms had struck illegal deals to fix the prices of eBooks in Europe.
The US case centres around the industry's ongoing concerns about the success of online retailer Amazon.com in selling electronic versions of many new best-sellers for just under $10 (£6.29) for its Kindle device.
" Apple facilitated the publisher defendants' collective effort to end retail price competition by co-ordinating their transition to an agency model across all retailers," according to the complaint filed in Manhattan federal court by the DOJ.
"To effectuate their conspiracy, the publisher defendants teamed up with defendant Apple, which shared the same goal of restraining retail price competition in the sale of eBooks," it added.
The publishers involved include Hachette Book Group, HarperCollins, MacMillan, Penguin Group, and Simon & Schuster.
But Apple's launch of the iPad forced a change in pricing for eBooks to an 'agency model' where publishers set prices and Apple is guaranteed a 30% cut, the lawsuit claims.
The model is seen by publishers as a defence against letting Amazon dominate the market, through its deep discounting, and is believed to have reduced the company's share of the eBook market from 90% to around 60%.
