Extended Black Friday and Cyber Monday sales saw a shopping surge for department stores, which raked in an almost 11% increase in sales on the previous year, official figures suggest.
The bumper sales moved from a one-day event, helping to spread spending over November and December last year, the Office for National Statistics (ONS) said.
Overall sales last month were up 2.6% compared to December 2014, but down by 1% on November last year.
Shoppers continued to take advantage of web-based deals, with online shopping accounting for around one in every £8 of retail spending last month, not counting fuel sales.
The average weekly spend online was £837.2m - and while the value of online sales was down 5.2% on November, it grew by 8.2% year-on-year.
Mild weather in December accounted for a 4.2% fall in clothing and footwear sales, the ONS said.
Retailers including Next, Marks & Spencer and Sports Direct have all blamed an unseasonably mild start to winter for poor trading over the festive season.
The amount spent fell by 1% compared to December 2014, and by 1.4% compared to November last year.
The ONS said: “We have seen a slightly different spending pattern in department stores in 2015 where higher year-on-year growth has been reported in December 2015 compared with December 2014.
“This suggests that the pattern of spending has changed between 2014 and 2015 as department stores moved from a one-day ‘Black Friday’ event to week-long events including ‘Cyber Monday’ and therefore spending was more spread out over the two months.”
Consumers benefited from price reductions, as average store prices fell by 3.2%, the 18th consecutive month of year-on-year price falls.