J Sainsbury defied the strong economic headwinds that are beginning to batter Tesco, its bigger rival, as it delivered solid interim profits and sounded a rare note of optimism for 2009.

Justin King, chief executive, said the company’s efforts to sell itself as an affordable supermarket in tougher times through its “Feed your family for a fiver” campaign, as well as its “Switch and save” push on its own-brand lines, was paying off.