Google will be hit by its biggest ever regulatory fine today as Brussels imposes a multibillion-euro penalty on the US tech group for abusing its dominant position in operating systems for mobile phones.

The European Commission finding is the most consequential move in its eight-year antitrust battle with Google. People familiar with the case said the fine would significantly outstrip the €2.4bn charge Brussels imposed on the group last year for favouring its own site in comparison shopping searches.

The decision takes aim at a core part of Google’s strategy over the past decade, outlawing restrictions on its Android operating system that allegedly entrenched its dominance in online search at a time when consumers were moving from desktop to mobile devices.