WASHINGTON — The Justice Department on Tuesday sued Google for abusing its dominance in online search and advertising — the government’s most significant attempt to protect competition since its groundbreaking case against Microsoft more than 20 years ago.

And it could just be an opening salvo. Other major tech companies including Apple, Amazon and Facebook are under investigation 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.”

Lawmakers and consumer advocates have long accused Google of abusing its dominance in online search and advertising. The case filed in federal court in Washington, D.C., alleges that Google uses billions of dollars collected from advertisers to pay phone manufacturers to ensure Google is the default search engine on browsers. That stifles competition and innovation from smaller upstart rivals to Google and harms consumers by reducing the quality of search and limiting privacy protections and alternative search options, the government alleges.

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 Google needs to be broken up to change its conduct. The Justice Department didn’t lay out specific remedies along those lines, although it asked the court to order structural relief “as needed to remedy any anticompetitive harm.”

That opens the door to possible fundamental changes such as a spinoff of the company’s Chrome browser.

Google vowed to defend itself and 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.”

Eleven states, all with Republican attorneys general, joined the federal government in the lawsuit. But several other states demurred.