The European Commission has begun an investigation to probe whether Apple and five prominent publishing houses have colluded to inflate the price of e-books.

The increasing popularity of devices like the iPad and Kindle have meant that e-book sales are expected to account for 10% of UK publishers’ £2.25bn revenues this year. The retailers are therefore up in arms against the publishers.

The commission issued a statement saying that it would target the five publishers, Hachette Livre, HarperCollins, Simon & Schuster, Pearson’s Penguin and the owner of the Macmillan imprint, Verlagsgruppe Georg von Holtzbrinck, to investigate whether they are party to anti-competitive practices, along with Apple.

EC’s competition spokeswoman Amelia Torres said this is an important issue for consumers, for people like us who love to read books, including on an electronic platform.

As Apple’s iBook store supplies e-books to the company’s iPad tablet computer and the iPhone, it also likely to come under the scrutiny of EC.