Australia's three major grocery retailers have admitted stocking seafood from a Thai company accused of using slave labour.

An investigation by the Associated Press has captured evidence of forced labour at a factory outside Bangkok, owned by seafood supplier Thai Union. Some of the workers are children who've said they work under the threat of violence.

Woolworths, Coles and Aldi have all told Fairfax they use Thai Union as a supplier, and have launched investigations…