Wal-Mart is moving towards a new flexible system of scheduling hourly workers based on the amount of traffic in stores in order to cut labour costs.

A spokesperson for the retailer, the largest private employer in the US, said that the new system would ensure stores are adequately staffed during busy periods while taking into account what hours employees prefer to work.

Previously, store managers calculated employee hours based on store sales, Wal-Mart told just-food. "The new system will take greater consideration of the hours staff want to work," the spokesperson said.

However, critics have suggested that the system will reduce the hours full-time staff are able to work and demand greater flexibility from employees.