US Internet giant Google had rejected EU allegations that it abused the market dominance of its hugely successful Android mobile phone operating system.
The rapsheet targets one of Google's most sensitive businesses, as smartphones become by far the dominant player over PCs and laptops.
"Android hasn't hurt competition, it's expanded it," said Kent Walker, senior vice president and general counsel of Google, in a blog.
Google was responding to a long list of charges involving Android that Margrethe Vestager, the EU's outspoken competition commissioner, filed in April.
They include the claim that the firm used practices such as making manufacturers pre-install its market-leading search engine as well as its Chrome browser as the default in their phones.
"The response we filed today shows how the Android ecosytem carefully balances the interests of users, developers, hardware makers and mobile operators," Walker said.
Google's response comes a week after the company rejected separate EU charges over online shopping and its advertising services in a series of rulings against US companies that has raised hackles across the Atlantic.
The Android charges are seen as especially sensitive for one of Google's most strategic businesses that could alter a global smartphone sector which has taken over traditional PC's as the biggest segment in the world of computing.
The case only pertains to Android-run phones, with the European Commission not considering Apple's iPhone as a factor in the case.
'Into compliance'
The EU in its charge sheet accused Google of obstructing innovation by giving unfair prominence to its own apps, especially its search engine, in deals with giant mobile manufacturers such as South Korea's Samsung or China's Huawei.
"No manufacturer is obliged to preload any Google apps on an Android phone," Google insisted.
Google is also accused of restricting manufacturers from installing rival versions or modifications of Android, an open source software operating system, on their phones.
The commission, through a spokesman, confirmed the receipt of Google's official response.
"As is standard practice, we will carefully consider Google's response before taking any decision on how to proceed and cannot at this stage prejudge the final outcome of the investigation," it said.
Google critics rejected the company's arguments.
"Google imposes severe sanctions on those who defy its insistence on conformity," said Thomas Vinje, legal counsel to FairSearch, a group that represents many of the complainants in the case.
"This is a problem that law enforcement can solve, by acting to bring Google into compliance with competition law," he added.
Complainants who brought the case to the EU include Yandez, a Russia-based search engine that says Google is stopping it from expanding beyond Russia.
They also include telecom companies that are looking to have better control of the Android software they provide on their smartphones.
But Google, which originally created Android, says limiting changes by companies to the system helps software developers so they do not have to make many versions of their apps to run on different versions of Android.
Developers of apps such as Spotify or WhatsApp, "depend on a stable and consistent framework to do their work," Google said.
