The BRC/Springboard Footfall Monitor in September showed a 2.4% drop when measured against a year ago, down on the 0.9% fall in August. This compares with particularly strong figures a year ago when footfall rose 0.5% in September 2012.
High street footfall was 2.7% lower than a year ago, falling sharply from the 0.6% decline in August. After five months of positive growth, footfall in out-of-town locations fell 1.3%.
Footfall in shopping centre locations fell 2.9% compared with a year earlier, the twelfth consecutive month to report a decline in footfall.
All regions and nations reported a decline in footfall in September. The West Midlands and the South West were hardest-hit with footfall falling 3.5% and 5.5% respectively.
Helen Dickinson, British Retail Consortium Director General, said: "Negative numbers across the UK are clearly a concern this close to Christmas, but there are a few factors at play.
"We're comparing against a very strong September in 2012, when the post-Olympic period coupled with a cold snap unleashed pent-up demand for shopping trips to stock up on warmer clothing and back-to-school items. In contrast, this year's milder September has slowed the uptake of Autumn ranges, a trend reflected in our sales figures last week.
"The sense of tentative optimism is continuing to take hold in the wider economy, but many of us remain cautious and keen to manage our budgets in the run-up to the festive season. Retailers will continue to monitor the mood and respond to customer demand accordingly as they prepare for the all-important countdown to Christmas."