Ten Los Angeles based garment contractors making clothes for retailers including Dillard's, Forever 21, Ross Stores and Urban Outfitters have been accused of serious labour violations.

The firms were inspected during a sweep of a single building in the Los Angeles Fashion District earlier this year by the US Department of Labor's Wage and Hour Division and the California Division of Labor Standards Enforcement.

Investigators found violations of the Fair Labor Standards Act's (FLSA) minimum wage, overtime and record-keeping provisions - including more than $326,200 owed in back wages to 185 employees.

Other retailers who sourced from the firms include Aldo Group, Burlington Coat Factory Warehouse, Charlotte Russe, Frasier Clothing (Susan Lawrence), HSN (Home Shopping Network), Rainbow Apparel, TJX Cos and Wet Seal Inc.

"The extent of the violations discovered by these investigations was disappointing," said Secretary of Labor Hilda Solis.

"Retailers need to actively ensure that clothes produced in the US for sale to the American public are made by workers who are paid at least the US minimum wage and proper overtime."

Investigators found many garment employees were paid a piece rate - that is, paid for each piece they sewed or cut - without regard to minimum wage or overtime pay requirements.

On average, workers' wages amounted to less than $6.50 per hour - well below the federal minimum wage of $7.25 per hour and the California minimum wage of $8 per hour.

None of the workers received the overtime premium of time and one-half their regular rates of pay for hours worked over 40 per week, as required under the FLSA.

Significant record-keeping violations also were disclosed, including falsified time cards and under-reporting or failing to maintain accurate records of actual hours worked by garment employees.