The suit says Google made deals to shut out competitors and set out to lock out rivals by muscling its search and advertising systems into users' everyday appliances.
Alphabet Inc's Google has faced its third major lawsuit as a group of 38 US states and territories filed an antitrust complaint accusing Google of seeking to extend its search monopoly to dominate smart speakers, televisions, and cars.
The states are asking for their lawsuit to 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.
'Google prevents competitors'
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," said Iowa Attorney General Tom Miller.
Google did not immediately respond to a request for comment.
Google shares were down 0.8 percent on Thursday afternoon.
The federal government's complaint was joined by 11 states and accused the $1 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.
The lawsuits mark a rare moment of agreement between Democrats and the Trump administration, whose criticisms seem to focus less on antitrust concerns and more on allegations that the platforms stifle conservative voices. Both moderate and progressive Democrats have praised the government's lawsuit.
The lawsuit was joined by the attorneys general of Alaska, Arizona, Connecticut, Delaware, Hawaii, Iowa, Idaho, Illinois, Kansas, Maine, Maryland, Massachusetts, Minnesota, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont, Virginia, W ashington, West Virginia and Wyoming.
Google did not respond to a request for comment.