San Francisco, In the biggest antitrust case against a tech company in two decades, the US Department of Justice and 11 state Attorneys General on Tuesday sued monopolist Google, alleging the tech giant has abused its market position in the domain of online search.

Charging the tech giant with anticompetitive practices in search and search advertising, the civil antitrust lawsuit was filed in the US District Court for the District of Columbia to stop Google from "unlawfully maintaining monopolies through anticompetitive and exclusionary practices in the search and search advertising markets and to remedy the competitive harms".

"Competition in this industry is vitally important, which is why today's challenge against Google -- the gatekeeper of the Internet -- for violating antitrust laws is a monumental case both for the Department of Justice and for the American people," said Attorney General William Barr.

"This lawsuit strikes at the heart of Google's grip over the internet for millions of American consumers, advertisers, small businesses and entrepreneurs beholden to an unlawful monopolist," Barr said in a statement.

Google reacted, saying the lawsuit by the Department of Justice is deeply flawed because "people use Google because they choose to, not because they're forced to, or because they can't find alternatives".

"This lawsuit would do nothing to help consumers. To the contrary, it would artificially prop up lower-quality search alternatives, raise phone prices, and make it harder for people to get the search services they want to use," argued Kent Walker, SVP Global Affairs and Chief Legal Officer at Google.

The US Department of Justice said that as one of the wealthiest companies on the planet with a market value of $1 trillion, Google is the monopoly gatekeeper to the internet for billions of users and countless advertisers worldwide.

"For years, Google has accounted for almost 90 per cent of all search queries in the United States and has used anticompetitive tactics to maintain and extend its monopolies in search and search advertising," it said.

Google said it is confident that a court will conclude that this suit doesn't square with either the facts or the law.

"American antitrust law is designed to promote innovation and help consumers, not tilt the playing field in favour of particular competitors or make it harder for people to get the services they want," Walker noted.

A Congressional report published earlier this month accused Google of favouring its own products in search results, a similar charge levied by the anti-trust competition authorities in Europe.

Last year, the EU antitrust regulators fined Google's parent company Alphabet $1.7 billion for unfairly restricting rivals from displaying ads on its platform via third parties using its AdSense tool. Google was also fined a record $5 billion by European antitrust authorities in 2018.

The antitrust case against Google is the biggest one against a tech company since the Microsoft case in 1998.

The participating state Attorneys General offices represent Arkansas, Florida, Georgia, Indiana, Kentucky, Louisiana, Mississippi, Missouri, Montana, South Carolina, and Texas.

The complaint alleged that Google has entered into a series of "exclusionary agreements" that collectively lock up the primary avenues through which users access search engines, and thus the internet.

This requires that Google "be set as the preset default general search engine on billions of mobile devices and computers worldwide and, in many cases, prohibiting pre-installation of a competitor".

The complaint alleged that Google's anticompetitive practices have had harmful effects on competition and consumers.

The tech giant said that the bigger point is that people don't use Google because they have to, they use it because they choose to.