Online fast-fashion giant Shein has filed another lawsuit against competitor Temu, accusing the China-founded shopping platform of stealing its designs, copying its product images and engaging in other types of fraud.

The complaint filed in a Washington federal court this week alleges that Temu, which has grown in popularity in the United States, has subsidized its low prices by encouraging sellers to offer counterfeited items, stolen designs and substandard products.

The allegations come as Shein itself is the target of lawsuits from brands and designers that have accused the company of stealing their designs and selling copycat items on its e-commerce site.

Asked for comment about the new lawsuit, a Temu spokesperson said in a prepared statement that Shein's "audacity is unbelievable."

"Shein, buried under its own mountain of IP lawsuits, has the nerve to fabricate accusations against others for the very misconduct they're repeatedly sued for," the spokesperson said.

The new lawsuit against Temu represents an escalation of the ongoing feud between the two companies, which have sued each other in U.S. courts before.

Temu, a platform owned by Chinese e-commerce company PDD Holdings, alleged in a previous lawsuit that Shein compelled clothing manufacturers to submit to unfair supply chain arrangements to prevent them from working with Temu.

Shein, which was founded in China but is now based in Singapore, accused Temu in court of engaging in deceptive business practices and misleading consumers by creating impostor accounts on social media that used Shein's name but directed people to Temu's platform.

The companies dropped those lawsuits in October. Temu sued Shein again in December, accusing its rival of employing "mafia-style intimidation" of suppliers to hamper its growth in the U.S.

Attorneys for Shein wrote in the new complaint that at least one Temu employee stole "valuable trade secrets" from Shein that identify best-selling products and internal pricing information.

They also claimed again that Temu falsely presented itself as Shein through impostor X accounts that directed customers to Temu's site. They further alleged Temu has engaged in similar practices through sponsored Google ads.