Shop prices were 2.1% lower in November compared to a year ago, dragged down by intensifying Black Friday competition and early discounting.
Non-food prices fell by 3.3% year-on-year, with clothing and electricals leading the way, according data from the British Retail Consortium and Nielsen.
It follows an overall drop of 1.8% in October, and marks the 31st consecutive month of falling retail prices. It also marks an acceleration on the 2.7% decline in non-food prices.
The period, from November 9 to 13, does not count Black Friday, which fell on November 27. However, the BRC said many retailers opted to cut prices in the run-up to the sales weekend, which also included Cyber Monday.
Nielsen head of retailer and business insight Mike Watkins said falling prices will be “another welcome boost for shoppers” as they plan their Christmas spend.
British Retail Consortium director general Helen Dickinson said: “This trading environment should be considered with the impact of the industry’s regulatory burden.”
Referring to Government announcements made since the general election in May, such as the introduction of the national living wage next April, she added: “BRC analysis shows that the combined cost of policy announcements since the General Election adds up to approximately £14bn over the next five years.”