The US government has filed an antitrust lawsuit against Google for allegedly violating competition law to preserve an illegal monopoly over internet searches and advertising.

The Justice Department and 11 states have banded together to accuse the tech giant of abusing its position to become the “monopoly gatekeeper for the internet”.

The charges, filed in a federal court, focuses on how Google spends billions of dollars every year to ensure that when people first connect to the internet – whether that be on their iPhones and other devices – its search engine is the default option.

This is allowing Google to own or control the distribution channels for about 80 per cent of search queries in the US, said Ryan Shores, the Justice Department’s senior advisor for tech industries.

“Google’s conduct is illegal under traditional antitrust principles and must be stopped,” Mr Shores said.

He claims the $US1 trillion ($A1.4 trillion) company acted unlawfully to maintain its position in search and search advertising on the internet.

“We’re asking the court to break Google’s grip on search distribution so that competition and innovation can take hold,” Mr Shores said.

The Justice Department is hoping to crack down on the scale and power of Google’s control over the search market in what has been deemed the biggest antitrust case in a generation.

“Countless advertisers must pay a toll to Google’s search advertising and general search text advertising monopolies,” the complaint reads.

“American consumers are forced to accept Google’s policies, privacy practices, and use of personal data; and new companies with innovative business models cannot emerge from Google’s long shadow.”

Google called the lawsuit “deeply flawed,” adding that people “use Google because they choose to – not because they’re forced to or because they can’t find alternatives”.

But without a court order, it’s feared Google will “continue executing its anti-competitive strategy, crippling the competitive process, reducing consumer choice and stifling innovation”, the lawsuit claims.

The complaint says that Google has nearly 90 per cent of all general search engine queries in the United States and almost 95 per cent of searches on mobile.

It is unclear exactly if the department is seeking a break-up or another remedy.

“Nothing is off the table but a question of remedies is best addressed by the court after it’s had a chance to hear all the evidence,” Mr Shore said.

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The complaint pointed to the billions of dollars that Google pays to smartphone makers such as Apple, Samsung and others to make Google’s search engine the default on their devices.

This means that rival search engines never get the scale they need to improve their algorithms and grow, the complaint said.

“The end result is that no one can feasibly challenge Google’s dominance in search and search advertising,” Attorney General Bill Barr said.

In its complaint, the Justice Department said that people in the US were hurt by Google’s actions.

In its “request for relief,” it said it was seeking “structural relief as needed to cure any anti-competitive harm”.

“Structural relief” in antitrust matters generally means the sale of an asset.

“Ultimately it is consumers and advertisers that suffer from less choice, less innovation and less competitive advertising prices,” the lawsuit states.

“So we are asking the court to break Google’s grip on search distribution so the competition and innovation can take hold.”

Republican Senator Josh Hawley, a vociferous Google critic, accused the company of keeping power through “illegal means” and called the lawsuit “the most important antitrust case in a generation”.

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US Senator Elizabeth Warren tweeted on September 10, using the hash tag #BreakUpBigTech, that she wanted “swift, aggressive action”.

Coming just days before the US presidential election, the filing’s timing could be seen as a political gesture since it fulfils a promise made by Trump to his supporters to hold certain companies to account for allegedly stifling conservative voices.

-with AAP