Its latest distributive trades survey found 24% of retailers reporting a rise in volumes, while 39% said sales had fallen.
The balance of -15% is the lowest since May 2010 but only slightly down on August.
The three-month average – which irons out seasonal volatility – was -11%, the fastest rate of decline since August 2009.
Judith McKenna, chief operating officer at Asda and chair of the CBI distributive trades panel, said: "High street sales are sluggish but appear to be stabilising.
"Shoppers are still clamping down on discretionary spending and focused on buying the basics at the best price."