The US Department of Justice sued Apple on Thursday for illegally maintaining a monopoly for its iPhone by stifling competition and imposing exorbitant costs on consumers.

The lawsuit, brought also by 17 US States, attacked the iPhone for raking in hundreds of billions of dollars by making it difficult for consumers to switch away from Apple to cheaper smartphones and devices.

The long-anticipated case against Apple sees the company founded by Steve Jobs clash with Washington after largely escaping US government scrutiny for nearly a half century.

At the heart of the case is Apple’s app store which sets strict and at times opaque conditions on firms and developers seeking to reach the iPhone’s 136 million US users.

According to the lawsuit, these rules and decisions have been designed to force Apple users into staying in the Apple ecosystem and buying the company’s expensive hardware, the iPhone.

“Consumers should not have to pay higher prices because companies violate the antitrust laws,” said Attorney General Merrick Garland. “If left unchallenged, Apple will only continue to strengthen its smartphone monopoly,” he added.

The far-reaching case singled out practices that it said was making Apple richer to the detriment of advancing innovation and technology for consumers.

In a statement, Apple denied the charges, saying it was “wrong on the facts and the law, and we will vigorously defend against it”.