Brussels has accused Google of violating antitrust rules in Europe via its Android operating system.
The European Competition Commission has filed formal charges against the company, which it believes "implemented a strategy" on mobile that favoured its own search.
Competition chief Margrethe Vestager said:
"A competitive mobile internet sector is increasingly important for consumers and businesses in Europe. Based on our investigation thus far, we believe that Google's behaviour denies consumers a wider choice of mobile apps and services and stands in the way of innovation by other players, in breach of EU antitrust rules.
"These rules apply to all companies active in Europe. Google now has the opportunity to reply to the Commission's concerns."
Google has been asked to respond to the official Statement of Objections, which details the claims against it, including that it broke the rules by:
- Requiring manufacturers to pre-install its search and browser apps, and requiring them to be set as default as part of licencing agreements.
- Stopping manufacturers from selling devices which run on competing operating systems but that are based on Android's open source code.
- Handing "financial incentives" to manufacturers and mobile networks on the condition that they exclusively pre-installed Google Search on devices.
The investigation into Android was first opened last year.
Responding to the claims, Google said: "We take these concerns seriously, but we also believe that our business model keeps manufacturers’ costs low and their flexibility high, while giving consumers unprecedented control of their mobile devices."
"Our partner agreements have helped foster a remarkable - and, importantly, sustainable - ecosystem, based on open-source software and open innovation.
"We look forward to working with the European Commission to demonstrate the careful way we’ve designed the Android model in a way that’s good for competition and for consumers," said Google's senior vice president and general council Kent Walker.
In a point by point rebuttal, Google said in a blog post that partner agreements are entirely voluntary and anyone can use Android without Google, such as Amazon does, while it pointed out that many apps such as Facebook and Amazon come pre-installed.
In a press conference, Vestager addressed why Apple was not under investigation, noting Apple does not licence its iOS operating system to other phone manufacturers.