Western Australia's trading hours debate has been reignited by the head of one of the country's most powerful business lobby groups, who described them as "archaic" and suggested they were hurting productivity growth.

Speaking at a British Australian Chamber of Commerce event in Perth on Tuesday, Business Council chief executive Jennifer Westacott said productivity growth in Australia was stagnant and if governments wanted wages to grow, productivity needed to grow as well.

Retail trading hours have flared up again after comments from Business Council of Australia Jennifer Westacott. Credit:Jim Rice

Ms Westacott said one impediment was restricting the hours retail businesses could operate and WA was a culprit.

"Shoppers can go online 24 hours a day, seven days a week but as you are painfully aware in Western Australia, shops still have archaic trading hours," she said.