The European Union Commission has launched a formal antitrust investigation into Amazon’s ebook business, following a similar probe into Google’s practices in April.
The Commission said that Amazon had deals with publishers which make it more difficult for other ebook distributors to compete with online retail services.
“Amazon has developed a successful business that offers consumers a comprehensive service, including for e-books,” Competition Commissioner Margrethe Vestager said in a statement.
“Our investigation does not call that into question. However, it is my duty to make sure that Amazon's arrangements with publishers are not harmful to consumers, by preventing other e-book distributors from innovating and competing effectively with Amazon.”
According to the commission, Amazon has clauses in these deals which require publishers to inform the company about more favourable terms offered to them.
In April, the EU opened a probe into Google’s business practices regarding its online search services, claiming that the web giant favours its own shopping service.
EU antitrust executives are also investigating Apple’s tax affairs, as well as the Starbucks café chain.
President Barack Obama complained earlier this year that Europe is turning to protectionism against the US tech sector while its administration is pushing a transatlantic free trade deal.