The states are asking for their lawsuit be consolidated with one filed by the Justice Department in October, according to a statement from the Colorado attorney general's office.

The complaint focuses on Google's search business and search advertising, as well as what they said was an effort by Google to use exclusionary agreements to also dominate newer technologies.

This would exclude, for example, competing virtual assistant technology such as Amazon.com Inc's Alexa.

The accusation builds on concerns publicly expressed by speaker maker Sonos and other companies that say Google has acted unfairly to grow its market power.

"Google is preventing competitors in the voice assistant market from reaching consumers through connected cars, which stand to be a significant way the internet is accessed in the near future," Iowa Attorney General Tom Miller said.

Google shares edged slightly lower after news of the latest lawsuit broke.

The federal government's complaint was joined by 11 states and accused the $US1 trillion ($A1.3 trillion) giant of acting unlawfully to maintain its position in search and advertising on the internet.

On Wednesday, a group of Republican attorneys general led by Texas filed a separate lawsuit focused on Google's dominance of digital advertising.

These lawsuits, in addition to two filed against social media giant Facebook Inc this month, promise to be the biggest antitrust cases in a generation, as big as the lawsuit against Microsoft filed in 1998.

That lawsuit was credited with clearing the way for the explosive growth of the internet.

Australian Associated Press