UK retail sales fell last month as snow and concerns about job security hit consumer spending, the British Retail Consortium (BRC) has said.
The BRC's data shows that sales declined 0.3% on a like-for-like basis - which excludes store openings and closures - compared with December 2009.
"The unusually early winter weather made a difficult Christmas worse for retailers," added the BRC.
While food and drink sales rose, the increase was less than last year.
"Christmas was not a complete disaster but it was impacted by the snow, which impacted certain retailers more than others," Helen Dickenson, head of retail at consultants KPMG, which helped to compile the survey, told the BBC.
"There was a big difference between how the food sector performed and how the non-food sector performed.
"Outside food, like-for-like sales were either flat or falling during the course of December."
The BRC said like-for-like food sales increased by 2.1% in the October-to-December period compared with a year earlier. It did not release a figure for December on its own.
Food sales were led by Christmas food and drink items, but also households stocking up on soups and ingredients for warming stews in the cold weather.
Like-for-like food sales in the October-to-December period in 2009 had risen by 2.6%.
Like-for-like sales of non-food items fell by 0.8% in the final quarter of 2010 compared with a year ago. A year earlier they had risen by 3.8%.
Stephen Robertson, BRC director general, said: "With mounting concerns about the impact of spending cuts and the wider economy, sales growth has been weak since last summer.
"December was always likely to be similarly unspectacular, but the snow and ice dealt an extra blow to business for many retailers."
December's 0.3% fall in like-for-like sales was the first decline reported by the BRC since April 2010.
Internet and mail order sales were 18% higher than a year before in December. However, this was a slowdown on the 27% growth recorded in December 2009, the BRC figures showed.
The UK's largest retailers are currently in the process of reporting their Christmas trading figures, and it has been a mixed picture so far.
While the likes of Morrisons, Waitrose, Ocado, and JD Sports saw sales rise, they fell at HMV and Mothercare.
Mr Robertson added: "Generally, people did spend on food for the big day.
"They had a celebration, but a combination of weather and worries led them to cut back on presents.
"With the big day over, there was a rush to the shops for discounted sales items, but customers hit the brakes on buying food and drink."
The BRC's figures came as the British Chambers of Commerce said the rate of UK economic growth likely slowed in the last quarter of 2010 because of weakness in the service sector, which includes retail.