Google has been fined a record $5 billion by the European competition watchdog for abusing the dominance of its mobile operating system, Android.

Google is accused of forcing smartphone makers like Samsung and Huawei to preinstall its services, such as Google Search and Google Maps, on Android.

Google says it will appeal the decision.

Google has been fined a record 4.3 billion euros ($5 billion/£3.8 billion) by Europe's competition watchdog for abusing its dominant Android mobile operating system to cement the popularity of Google apps and services.

It's the biggest antitrust fine given by Europe's competition regulator against a single firm, cementing the reputation of the European Union's competition commissioner, Margrethe Vestager, as Silicon Valley's policewoman. Google said it would appeal the decision.

"Today, the commission ... rules Google has engaged in illegal practices to cement its dominant market position in internet search," Vestager said on Wednesday. "It must put an effective end to this conduct within 90 days or face penalty payments."

The European Commission found Google had used Android, the most popular mobile software globally, to reinforce its dominance in search.

Specifically, it said:

Google forced phone makers to preinstall its Chrome browser and its Search app as a condition for accessing the Play app store.

Google illegally paid manufacturers to preinstall its Search app exclusively, protecting its search business from competition.

Google prevented Android phone makers from selling devices that run "forked" versions of the operating system.

Android is the most popular mobile operating system in the world. Mark Blinch/Reuters

Google said Android had created choice and not hindered it. The company said it would appeal the commission's decision.

Europe's competition watchdog has been investigating Google for more than three years. The firm was fined 2.4 billion euros (£2.1 billion/$2.7 billion) last year for promoting its own shopping service in search. Google is appealing that fine. A third investigation is also underway over whether Google's AdSense technology protects its dominant position in online advertising.

It's also the latest in a long line of penalties and investigations into Silicon Valley firms by Vestager, who has imposed the record fines against Google, a fine against Facebook over its WhatsApp acquisition, and an investigation into Apple over its purchase of the music app Shazam.