Fast fashion behemoth Shein had a second federal civil lawsuit filed against it in a week as rival down-market retailer Temu filed an anti-trust action in the U.S. District Court of Massachusetts.

The Temu lawsuit alleges that Shein used monopolistic powers to keep the rival out of the ultra-fast fashion marketplace, violating the Sherman Anti-Trust Act as well as other torts.

“Having controlled nearly the entire market in ultra-fast fashion in the U.S. between early 2020 and Temu’s entry in late 2022, Shein was and is a monopolist,” the lawsuit says. “Shein has attempted to maintain its monopoly by means of its anticompetitive scheme, desperate to avoid the robust competition Temu brought to the market.”

A Shein spokesperson told Reuters that the lawsuit was, “without merit and we will vigorously defend ourselves.”

USA Today has reached out to Shein regarding the lawsuit but have yet to receive a response.

Shein in court on both coasts, faces RICO lawsuit in California

The Massachusetts lawsuit comes on the heels of a separate civil filing by three fashion designers in the District Court for the Central District of California alleging that the Chinese retailer violated the Racketeer Influenced and Corrupt Organizations Act, better known as RICO.

The lawsuit alleges that Shein stole the intellectual property of the designers and that the company uses a, “byzantine shell game of a corporate structure,” to avoid lawsuits.

“Shein has grown rich by committing individual infringements over and over again, as part of a long and continuous pattern of racketeering, which shows no sign of abating,” the lawsuit states.