UK retail sale values sank 0.6% in October compared to last year, with the British Retail Consortium warning sales were "worryingly weak" in the approach to Christmas.
In October last year, sales values had risen by 0.8%. On a total basis sales were up by 1.5% in October this year, but in the same month last year sales had risen by 2.4%.
The BRC warned book sales remained "very tough and well below their year-earlier level".
"Print books suffered from the shift to e-books, with paperback fiction hardest hit. Terry Pratchett’s Snuff was the top seller, followed by the ever-popular Guinness Book of Records," the BRC said.
Helen Dickinson, head of retail at KPMG, said: "With so much uncertainty across European and global markets, UK consumers remain reticent as their personal finances become harder to manage.
"The beginning of the month continued with the trend we saw at the end of September: the warm weather helped to boost food sales to the detriment of clothing and other non-food sectors. But one constant remains: to whatever extent sales are being made, margins and hence profits are being impacted to stimulate demand as retailers strive to cope with the new reality.
"The success of the Christmas season for retailers hangs in the balance as October’s results do not set a strong foundation."