The Federal Trade Commission on Wednesday sued Amazon for illegally inducing customers to join its Prime service after which hindering them from canceling the subscription, essentially the most aggressive motion in opposition to the corporate thus far by the company’s chair, Lina Khan.

The lawsuit, filed in U.S. District Court for the Western District of Washington, argues that Amazon had used design techniques on its web site often known as “dark patterns” to nudge individuals into subscribing to Prime, the F.T.C. stated in a launch. And when customers needed to cancel, they needed to undergo a byzantine course of to take action.

“Amazon tricked and trapped people into recurring subscriptions without their consent, not only frustrating users but also costing them significant money,” Ms. Khan stated in an announcement.

Amazon didn’t instantly reply to a request for remark.

The lawsuit was the primary time that the F.T.C. has taken Amazon to court docket below Ms. Khan, who rose to fame with a viral critique of the corporate and who’s ramping up scrutiny of the e-commerce big. Ms. Khan has stated the ability that huge tech corporations have over on-line commerce requires regulators to be way more aggressive and has begun taking actions in opposition to them.

Under Ms. Khan, the F.T.C. continued a lawsuit in opposition to Meta, arguing it minimize off nascent opponents by shopping for Instagram and WhatsApp, and sued to dam Microsoft’s blockbuster $69 billion deal for the online game writer Activision Blizzard.

Ms. Khan has but to deliver the type of sweeping antitrust case in opposition to Amazon that the corporate’s critics demand. The F.T.C.’s antitrust bureau has been investigating Amazon’s practices for years and observers are intently watching how she is going to transfer ahead with their findings.

The lawsuit is an element of a bigger effort by regulators to restrict the ability of tech giants together with Amazon, Apple, Google, Microsoft and Meta, Facebook’s father or mother firm. The Department of Justice has in recent times filed a number of antitrust cases in opposition to Google.

Amazon has lately settled circumstances with the F.T.C. that started earlier than Ms. Khan’s tenure. The firm agreed to pay $25 million final month to settle F.T.C. claims that Amazon’s Alexa dwelling assistant gadgets had illegally collected youngsters’s knowledge. The company additionally settled one other privateness case with Amazon’s Ring dwelling safety subsidiary.

Amazon Prime has for years attracted subscribers with guarantees of free expedited transport, entry to a streaming video library and different advantages. In 2021, the corporate stated that it had greater than 200 million members in this system, which prices $139 a 12 months. Customers final 12 months spent $35 billion on Amazon subscriptions, primarily Prime memberships, in response to the corporate’s monetary disclosures.

On Wednesday, the F.T.C. stated that Amazon had made it significantly tough to buy a product in its retailer with out additionally subscribing to Prime whereas trying out. The company stated Amazon made it arduous for customers to seek out the web page that allowed them to cancel the service. Once they did discover it, Amazon bombarded them with presents supposed to make them change their thoughts.

The lawsuit follows years of media and activist consideration on how arduous it’s to cancel Prime. In a 2021 grievance to the District of Columbia lawyer normal, the Electronic Privacy Information Center, an advocacy group, stated that Amazon had used manipulative designs to “frustrate the intentions of users who intend to cancel their Amazon Prime subscriptions.”

The F.T.C. has lately pledged to crack down on designs meant to nudge customers or confound their efforts to cancel a service.

“While dark patterns may manipulate consumers in stealth, these practices are squarely on the F.T.C.’s radar,” the company stated in a 2022 report.

Critics think about Prime central to Amazon’s dominance as a result of it retains prospects inside the corporate’s retail retailer by providing them different perks, like entry to Amazon streaming exclusives comparable to “Tom Clancy’s Jack Ryan” and “The Lord of the Rings: The Rings of Power.”

Amazon has stated that Prime supplies advantages for customers. When the corporate lobbied in recent times in opposition to reforms to antitrust legal guidelines centered on the tech giants, it usually informed lawmakers and the media that the modifications would hobble Prime.