Lululemon Athletica – founded in 1998 – is suing an array of websites that are selling knock-off yoga pants and infringing on the trademark of the well-established brand.

The lawsuit, filed on Monday in a Chicago Federal Court, claims hundreds of websites are infringing on Lululemon’s trademark and, in turn, diluting their brand by deceiving consumers with fake sportswear and apparel offered with huge discounts. According to the lawsuit, the majority of the counterfeiters are based in China and ‘foreign jurisdictions’. The websites allegedly have “virtually identical” layouts and include many misspellings and grammar mistakes.

“The success of the Lululemon brand has resulted in its significant counterfeiting,” the lawsuit says. “Despite Lululemon’s enforcement efforts, defendants have persisted in creating the . . . internet stores.”

Lululemon and a Chicago attorney representing the company in the lawsuit declined to comment Tuesday.