Sainsbury said its like-for-like (LFL) retail sales fell 1.1%, excluding fuel, in the 16 weeks to Sept. 24, and, including fuel, were down 0.5%.
Total retail sales eased 0.4% excluding fuel, and were flat if fuel was included.
"We continue to make progress against our strategy and, while like-for-like sales were down 1.1 per cent (excl. fuel), driven by food price deflation, we delivered like-for-like transaction growth across all channels and total volume growth," said CEO Mike Coupe in a statement.
"This shows that customers are consistently choosing Sainsbury's for the choice, quality, value and customer service we offer," he added.
"We have made further investment in everyday low prices and continue to improve the quality of our products. Our general merchandise and clothing offer is popular with customers and the acquisition of Home Retail Group will accelerate our multi-product, multi-channel strategy.
"We will open 200 new digital collection points by the end of the year and already have 15 Argos Digital stores open in Sainsbury's stores so customers can shop 90,000 products whenever and wherever they want.
"We expect the market to remain competitive and the effect of the devaluation of sterling remains unclear.
"However, Sainsbury's is well positioned to navigate the changing marketplace and we are confident that our strategy will enable us to continue to outperform our major peers."