California garment workers have quadrupled the number of wage claims filed since the passage of an anti-sweatshop law in 1999 according to a report released on Wednesday.

The study by the Asian Pacific American Legal Center of Southern California says that between 2001 and 2004, workers filed 2,282 claims, compared with 565 between 1995 and 1998.

But it cautions that the average amount manufacturers paid to workers was just $673, and that overall, workers received an average of only 31 per cent of the money they seek from contractors and the manufacturers.

The study said wage violations continue in the industry, and that the state of California must do more to force employers to comply with minimum-wage laws.

The anti-sweatshop law AB 633 was introduced to help workers recover back wages from garment factories and from manufacturers that contract with the plants. It has had some success, with 75 per cent of workers being able to reach settlements of their claims.

The study - 'Reinforcing The Seams: Guaranteeing the Promise of California's Landmark Anti-Sweatshop Law' - was based on a sample of 208 wage claims filed between March 2001 and February 2004.