The Justice Department and 16 state attorneys general filed an antitrust lawsuit against Apple on Thursday, the federal government’s most significant challenge to the reach and influence of the company that has put iPhones in the hands of more than a billion people.

The government argued that Apple violated antitrust laws by preventing other companies from offering applications that compete with Apple products like its digital wallets, which could diminish the value of the iPhone. Apple’s policies hurt consumers and smaller companies that compete with some of Apple’s services, according to excerpts from the lawsuit released by the government, which was filed in the U.S. District Court for the District of New Jersey.

“Each step in Apple’s course of conduct built and reinforced the moat around its smartphone monopoly,” the government said in the lawsuit.

The lawsuit caps years of regulatory scrutiny of Apple’s wildly popular suite of devices and services, which have fueled its growth into a nearly $2.75 trillion public company that was for years the most valuable on the planet. It takes direct aim at the iPhone, Apple’s most popular device and most powerful business, and attacks the way the company has turned the billions of smartphones it has sold since 2007 into the centerpiece of its empire.

By tightly controlling the user experience on iPhones and other devices, Apple has created what critics call an uneven playing field, where it grants its own products and services access to core features that it denies rivals. Over the years, it has limited finance companies’ access to the phone’s payment chip and Bluetooth trackers from tapping into its location-service feature. It’s also easier for users to connect Apple products, like smartwatches and laptops, to the iPhone than to those made by other manufacturers.

The company says this makes its iPhones more secure than other smartphones. But app developers and rival device makers say Apple uses its power to crush competition.