The Office for National Statistics (ONS) said sales fell 3.7 per cent in December – the biggest monthly fall since January 2021 – compared to a rise of 1 per cent in November.
Officials also suggested the fall was due to shoppers getting their gift-buying done earlier in November to avoid disappointment due to supply chain disruption.
Non-food stores took some of the hardest hits, with volumes dropping 7.1 per cent across department stores, clothes outlets and homewares businesses.
There was a 4.7 per cent drop in fuel sales last month, as restrictions saw a return to work-from-home rules and fewer people travelled as Omicron led to large numbers of households self-isolating.
Food stores sales fell by 1 per cent, although they remained 2 per cent above pre-pandemic levels.
Data showed the number of shoppers heading to physical stores was below normal expectations for the busy festive period, with the ONS pointing out that footfall levels were 81 per cent of the levels seen in the week leading up to Christmas 2019.
By comparison, the proportion of online sales rose slightly in the month from 26.3 per cent of total sales in November to 26.6 per cent in December.
Sam Miley, senior economist at CEBR, added: “Retail sales volumes contracted sharply in December, as the emergence of the Omicron variant impacted consumer behaviour. These effects are expected to subside, however, given the recent fall in case numbers and changes to policy guidance.”