Three California law firms are seeking an injunction to stop the US retail chain Costco selling prawns unless they are labelled as the produce of slavery. The firms have filed a class action lawsuit against Costco and its Thai seafood supplier, alleging that Costco knowingly sold prawns from a supply chain tainted by slavery. The claim, lodged in the federal court in San Francisco on Wednesday, alleges that Costco has for several years bought and resold farmed prawns from the leading Thai food group CP Foods…that have sourced the raw material for their feed from ships manned by slaves…Costco said in a statement: “…Costco Wholesale has been working with and will continue to work with various stakeholders…to address the issues that have surfaced…[A]ll of our customers know that if they are dissatisfied with any purchase…they can return the item for a full refund.”…CP Foods said last year that it condemned all trafficking and slavery in the strongest possible terms…