Textile union chiefs on Monday expressed delight at securing the backing of Australia's biggest retailer Coles Myer in their fight against the exploitation of garment outworkers.

The Textile, Clothing and Footwear Union said the retail giant’s decision to endorse its ethical clothing code will allow it to check the firm’s suppliers and contractors to ensure labour and welfare compliance.

Union spokesman Barry Tubner said he is now confident other leading apparel chains will sign up to the new code over the next few months.

"It's a matter of putting in place a process where the union will physically go out and visit all these suppliers and their subcontractors, so that the retailers can be comfortable that the product... they sell isn't made from exploited labour," he said.

"This campaign has been going on for nearly 20 years and we're probably the closest we've ever come to being able to say that one day in the near future there won't be any exploited outworkers in Australia."

In September, three dozen leading retailers in New South Wales signed an anti-sweatshop agreement formed by the state government in a move designed to ensure their suppliers do not use exploitative work practices.