Google was sued for allegedly abusing its market power by forcing handheld device makers that use its Android operating system to also provide the search engine company's applications.
Google's requirements that manufacturers such as Samsung Electronics adopt less popular applications in order to use consumer favourites such as YouTube are "designed to maintain and extend its monopolies," according to a complaint filed on Thursday in federal court in San Jose, California.
The existence of the Android "mobile application distribution agreements," or MADAs, wasn't widely known until this year, when Harvard Business School professor Ben Edelman wrote about them on his blog and voiced concerns about anticompetitive behaviour similar to the claims in the lawsuit.
Worldwide, 78 per cent of smartphones were run on Android in the fourth quarter of 2013, according to IDC. Apple's iOS had 18 per cent of the market, while Windows had 3 per cent and BlackBerry had 0.6 per cent.
Google's expansion of its monopoly in search on smartphones, which helps through paid search-related advertisements to generate billions of dollars of profit a year, is "not merely a function of having built a better search engine," according to Thursday's complaint on behalf of consumers.
The "secret" MADAs require that each Android device maker "pre-loads onto prime screen real estate all of the apps in the suite, whether the manufacturer wants them or not," according to the complaint.
"Anyone can use Android without Google and anyone can use Google without Android," Matt Kallman, a spokesman for Mountain View, California-based Google, said in an email. "Since Android's introduction, greater competition in smartphones has given consumers more choices at lower prices."
Thursday's lawsuit was filed by the owner of an HTC EVO 3D mobile phone made in 2011 that runs on Android. The consumer argued that Google's restrictions on Android made the phone more expensive. Google's MADAs with Samsung and HTC were included as exhibits in the lawsuit.
The lawsuit includes a claim that Google's pressure tactics on manufacturers are currently under investigation by the European Union in response to a complaint by FairSearch.org, whose members include Microsoft and Oracle.
Edelman, who is a consultant to companies that compete with Google, said in a February blog post that copies of MADAs had been filed as exhibits in a 2012 trial between Google and Oracle over Android. He said on Thursday that the Android tie-ins foreclose competition and raise prices for both advertisers and consumers.
"Google did this through secret contract restrictions - documents that probably wouldn't have become widely available to the public had I not presented them on my site in February," he said in an email. "The secrecy is itself troubling - users see Google apps preinstalled and conclude that carriers and other users must think they're the best, when in fact Google apps are preinstalled only because Google insists that they be there."
Google has had previous run-ins over allegedly anti-competitive behaviour relating to search. The company ended a 20- month federal probe in 2013 over whether it unfairly skewed search results. It avoided a potentially costly legal battle with US regulators by pledging to change some business practices and settling allegations that it misused patents to thwart competitors in smartphone technology.
The firm said it would voluntarily remove restrictions on the use of its online search-advertising platform and offer companies the option of keeping their content out of Google's search results.
Hagens Berman Sobol Shapiro, the Seattle-based law firm that filed Thursday's complaint, represents plaintiffs in other big antitrust cases. In one complaint filed in March in San Francisco, the firm accused the National Collegiate Athletic Association and five regional football conferences of conspiring to cap the value of scholarships below the actual cost of college attendance to control costs.
The law firm is also handling a group lawsuit on behalf of consumers in federal court in New York alleging that Apple conspired with publishers to inflate electronic-book prices.