WASHINGTON — The Justice Department on Tuesday, Oct. 20, 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.

“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.”

The case filed in federal court in Washington, D.C., alleges 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 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.”

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 — Arkansas, Florida, Georgia, Indiana, Kentucky, Louisiana, Mississippi, Missouri, Montana, South Carolina and Texas — all with Republican attorneys general, joined the federal government in the lawsuit. But 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.

President Donald Trump’s administration has long had Google in its sights. One of Trump’s top economic advisers said two years ago the White House was considering whether Google searches should be subject to government regulation.

The Justice Department sought support for its suit from states across the country that share concerns about Google’s conduct. A bipartisan coalition of 50 U.S. states and territories, led by Texas Attorney General Ken Paxton, announced a year ago they were investigating Google’s business practices, citing “potential monopolistic behavior.”

Other major tech companies including Apple, Amazon and Facebook also are under investigation at the Justice Department and the Federal Trade Commission.