The DoJ said Google's market dominance was harmful to other business in the sector, and called for the company to be broken up.
The complaint, filed on Tuesday 23 January in a Virginia federal court, accuses Google of using “anti-competitive, exclusionary, and unlawful means to eliminate or severely diminish any threat to its dominance over digital advertising technologies”.
US Attorney General Merrick Garland added Google's actions had "weakened if not destroyed competition in the ad tech industry".
In response, Google accused the DoJ of "doubling down on a flawed argument".
The legal dispute is the agency’s first antitrust lawsuit against a tech giant under President Joe Biden and an escalation in legal pressure on one of the world’s biggest internet companies.
The lawsuit said Google had “corrupted legitimate competition in the ad tech industry by engaging in a systematic campaign to seize control of the wide swath of high...