According to the British Retail Consortium (BRC), the U.K. shop prices declined by 2.1% year-on-year in November, after a 1.8% decline in October.
The decline was mainly driven by a drop in non-food prices, which plunged 3.3% year-on-year in November.
Food prices fell at an annual rate of 0.3% in November.
"Although the survey period does not cover Black Friday, it is likely that some retailers were discounting early in November in order to spread consumer spending over a longer period," BRC Chief Executive, Helen Dickinson, said.