Google must stop giving financial incentives to handset manufacturers that pre-install Google Play and Google Search onto devices running Android, or risk a huge fine from the European Commission (EC).
The EC first began investigating Google in 2015 about the way in which the firm uses the Android platform to promote its other services, such as Search and YouTube, by pre-installing them on devices at the expense of rivals' services.
The EC sent a Statement of Objections to Google in April having ruled that the company was indeed acting in this way.
Reuters has now reported that it has seen the 150-document sent to Google setting out these concerns, and that it also shows the EU readying large fines against Google unless the company makes major changes to how it pushes Android onto the market via manufacturing partners.
This would include banning Google giving payments or discounts to mobile phone manufacturers in return for pre-installing the Play store and Google Search.
The EC also wants to prevent Google forcing smartphone makers to pre-install the firm's proprietary apps, if this restricts their ability to use competing operating systems based on Android.
The document said that Google "cannot punish or threaten" companies for not complying with its conditions, and that the firm could face a "large fine" because the anti-competitive practices, which started in January 2011, are still going on.
This fine would be based on the revenue Google generated from AdWords clicks in Europe, Google Search product queries, Play store apps purchases and AdMob's in-app advertisements.
"The EC intends to set the fine at a level which will be sufficient to ensure deterrence," the EC document explained.
Google said in a statement: "We look forward to showing the EC that we've designed the Android model in a way that's good for competition and consumers, and supports innovation across the region."
A separate document, also seen by Reuters, suggests that the EC could also fine Google in its investigation into the firm's allegedly anticompetitive Google Shopping business.
Additionally, Google could be forced to rank rival shopping services as equally as its own service.
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