LOS ANGELES — For two decades, Ziba Beauty salons have brought the Indian techniques of eyebrow threading and henna tattoos to a clientele that has included Madonna, Gwen Stefani, Salma Hayak and Naomi Campbell.

Ziba Chief Executive Sumita Batra, 39, and her staff have styled models for Vanity Fair and Rolling Stone magazines and TV shows “America’s Next Top Model” and “Extreme Makeover.”

But now Batra and her family partners are accused of building their business by exploiting workers, many of them female immigrants. Former Ziba workers recently filed a class action lawsuit alleging that the owners of the 11-store salon chain failed to give them the minimum wage, overtime compensation, and meal and rest breaks.