OAKLAND, Calif. (CN) — The advocacy group One Fair Wage is taking on the largest restaurant chain in America with a federal lawsuit challenging its policy of paying tipped workers less than minimum wage, claiming it leads directly to higher rates of sexual harassment and pay inequity for servers of color. Its lawsuit filed Thursday claims Darden Restaurant Group, which operates national chains like the Olive Garden and Longhorn Steakhouse, maintains a wage policy that forces workers to rely on tips to make up the bulk of their wages. This in turn puts servers at the mercy of potentially biased, racist or sexist customers who may be biased.