Google has been handed a €1.5bn (£1.3bn) fine by the EU regulators for stifling competition in the online advertising market which it dominates.

“Google has engaged in illegal practices when it comes to their search advertising brokering in order to cement its dominant poisition,” European competition commissioner Margrethe Vestager said on Tuesday.

It is the third largest fine that Google has received from EU regulators for flouting competition rules but could be more serious for the company as it goes to the heart of its advertising business.

The European Commission said Google abused its position to stifle innovation by restricting websites’ ability to display adverts from rival brokers.

Last year, Ms Margarethe Vestager imposed a record €4.3bn fine on Google for using its Android mobile operating system to block rivals.

By preinstalling its Chrome browser and Google search app on Android devices, the company had an unfair advantage over its rivals, EU enforcers said.

That followed a €2.4bn fine levied in 2017 for blocking rivals of shopping comparison websites.

The European Commission said the company had used the software to unfairly expand its search engine dominance and “denied European consumers the benefits of effective competition”.

The latest decision concerned Google’s AdSense business that lets web publishers place text ads on their websites, with the content of the ads based on results from search functions on their sites.

Google’s contracts prevented websites from choosing adverts brokered by competitors and therefore “prevented its rivals from having a chance to innovate and to compete in the market on their merits”, Ms Vestager said.

“Advertisers and website owners ... had less choice and likely faced higher prices that would be passed on to consumers.”

In a bid to placate the commission, which has led the fight against monopolistic behaviour by US technology giants, Google announced on Tuesday that it would let Android users know about the wide choice of browsers available on smartphones.

“This will involve asking users of existing and new Android devices in Europe which browser and search apps they would like to use,” the company said in a blog post.

Pressure is mounting on Google, Facebook and Twitter after the EU accused them last month of falling short on promises to combat fake news.