Spar's outsourced procurement team has warned retailers they are paying over the odds by buying services and goods not for resale direct.

Brightsourcing, founded by Somerfield's purchasing managers, was hired by Spar last year to improve its Smart Saving scheme.

Director Marcus Leyden said retailers could save between 5% and 20% of their annual procurement spend. "If your costs are, say, 10% more than they could be, you're wasting not only money but time, effort and energy," Leyden added.