A federal judge has ruled a group of garment workers suing fashion giant Donna Karan over alleged sweatshop conditions do not have to reveal their immigration status to the firm's lawyers.

The judge said he was worried such information could be used to "intimidate" the five workers. They claim they were cheated out of overtime and had to work in sweatshop conditions in plants owned by a Chinese couple who are co-defendants.

The lawsuit, which was filed two years ago, has been brought by the Asian American Legal Defense and Education Fund.