Led by Colorado's Attorney General Phil Weiser, the new legal action alleges Google illegally maintains monopoly power over search engines and related advertising "by stifling competition."
"Google’s anticompetitive actions have protected its general search monopolies and excluded rivals, depriving consumers of the benefits of competitive choices, forestalling innovation, and undermining new entry or expansion," Weiser said in a statement. "This lawsuit seeks to restore competition."
He added that consumers are "squeezed when they are deprived of choices in valued products and services."
This is the third major antitrust lawsuit leveled against the social media giant since October, after the Department of Justice announced a suit, and a coalition of ten Republican state attorneys general announced a suit Thursday over ads.
The latest lawsuit is similar to the DOJ's, but goes beyond to allege that Google engaged in a multi-pronged effort to maintain its monopoly. The states said they're bringing additional claims to combat what they called "a broader range of Google's illegal conduct."
"Google, one of the largest companies in the world, has methodically undertaken actions to entrench and reinforce its general search services and search-related advertising monopolies by stifling competition," the complaint states. "As the gateway to the internet, Google has systematically degraded the ability of other companies to access consumers."
The court documents state that 90% of internet searches use Google, and that, "Steadily and over the years, Google has expanded and refined the tactics it uses to harm competition."
"Instead of simply producing a better service that keeps consumers and advertisers loyal, Google focuses on building an impenetrable moat to protect its kingdom," the lawsuit states.
Adam Cohen, Google’s director of economic policy, responded to the suit in a blog post Thursday, highlighting how the search engine has improved over the past 20 years.
"To get more specifically to the issues raised in today’s lawsuit: it suggests we shouldn't have worked to make Search better and that we should, in fact, be less useful to you: When you search for local products and services, we show information that helps you connect with businesses directly and helps them reach more customers," Cohen wrote. "This lawsuit demands changes to the design of Google Search, requiring us to prominently feature online middlemen in place of direct connections to businesses."
"Redesigning Google Search this way would harm the quality of your search results. And it would come at the expense of businesses like retailers, restaurants, repair shops, airlines and hotels whose listings in Google help them get discovered, and connect directly with customers," he added. "They would have a harder time reaching new customers and competing against big commerce and travel platforms and other aggregators and middlemen."
Cohen added that scrutiny of big companies is important and Google is prepared to "answer questions and work through the issues."
"But this lawsuit seeks to redesign Search in ways that would deprive Americans of helpful information and hurt businesses’ ability to connect directly with customers," he wrote. "We look forward to making that case in court, while remaining focused on delivering a high-quality search experience for our users."
The attorneys general asked the court to halt Google’s allegedly illegal conduct and restore a competitive marketplace. The states also seek divestiture of assets as appropriate.
Thursday's suit against Google comes a little over a week after a coalition of 48 state attorneys general, led by New York's Letitia James, announced a separate antitrust lawsuit against fellow tech giant Facebook.
ABC News' Aaron Katersky reports for ABC News Radio: