WASHINGTON (AP) — The Justice Department on Tuesday sued Google for antitrust violations, alleging that it abused its dominance in online search and advertising to stifle competition and harm consumers.

The lawsuit marks the government’s most significant attempt to protect competition since its groundbreaking case against Microsoft more than 20 years ago. It could be an opening salvo ahead of other major government antitrust actions, given ongoing investigations of major tech companies including Apple, Amazon and Facebook at both the Justice Department and the Federal Trade Commission.

“Google is the gateway to the internet and a search advertising behemoth,” U.S. Deputy Attorney General Jeff Rosen told reporters. “It has maintained its monopoly power through exclusionary practices that are harmful to competition.”

Antitrust cases in the technology industry have to move quickly, he said. Otherwise “we could lose the next wave of innovation.”

Lawmakers and consumer advocates have long accused Google, whose corporate parent Alphabet Inc. has a market value just over $1 trillion, of abusing its dominance in online search and advertising to stifle competition and boost its profits. Critics contend that multibillion-dollar fines and mandated changes in Google’s practices imposed by European regulators in recent years weren’t severe enough and that structural changes are needed for Google to change its conduct.

The Justice Department isn’t seeking specific changes in Google’s structure or other remedies at this point, but isn’t ruling out seeking additional relief, officials said.

Google responded immediately via tweet: “Today’s lawsuit by the Department of Justice is deeply flawed. People use Google because they choose to — not because they’re forced to or because they can’t find alternatives.”

The case was filed in federal court in Washington, D.C. It alleges that Google uses billions of dollars collected from advertisers to pay phone manufacturers to ensure Google is the default search engine on browsers. Eleven states, all with Republican attorneys general, joined the federal government in the lawsuit.

But several other states demurred. The attorneys general of New York, Colorado, Iowa, Nebraska, North Carolina, Tennessee and Utah released a statement Monday saying they have not concluded their investigation into Google and would want to consolidate their case with the DOJ’s if they decided to file. “It’s a bipartisan statement,” said spokesman Fabien Levy of the New York State attorney general’s office. “There’s things that still need to be fleshed out, basically,”