Google has been fined €2.95bn (£2.5bn) by the EU for allegedly abusing its power in the ad tech sector - the technology which determines which adverts should be placed online and where.
The European Commission said on Friday the tech giant had breached competition laws by favouring its own products for displaying online ads, to the detriment of rivals.
It comes amid increased scrutiny by regulators worldwide over the tech giant's empire in online search and advertising.
Google told the BBC the Commission's decision was wrong and it would appeal.
It imposes an unjustified fine and requires changes that will hurt thousands of European businesses by making it harder for them to make money, said Lee-Anne Mulholland, global head of regulatory affairs at Google.
US President Donald Trump also attacked the decision, saying in a post on social media it was very unfair and threatening to launch an investigation over European tech practices that could lead to tariffs.
Earlier this week, the Commission denied reports it had delayed the announcement of Google's fine amid tensions over trade relations between the EU and the US.
In the Commission's decision on Friday, the Commission accused Google of self-preferencing its technology above others. It claimed Google had intentionally boosted its own advertising exchange, AdX, over competing exchanges, leading to higher costs for competitors and reduced revenues, which may have impacted consumers with increased prices.
As part of its findings, the regulator ordered Google to end such practices and pay the fine.
Third time rules broken
This fine marks one of the largest penalties the EU has imposed on tech companies for breaching competition rules. Previously, in 2018, the EU fined Google €4.34bn for antitrust violations related to its Android operating system.
Teresa Ribera, executive vice president of the Commission, stated that previous rulings informed the decision to increase the latest fine, noting it was the third instance of rule breaches by Google.
Ribera warned the tech giant that it had 60 days to address its practices, or the Commission would implement its own solutions, which may involve structural remedies such as divesting parts of its ad tech business.
