Retail sales fell in May by 0.5%, following a rise of 0.4% in April, with consumer confidence falling and food purchases declining.
The Office for National Statistics' figures showed a 1.6% reduction in food spend in shops, linked to the rising cost in food prices and the cost of living.
Supermarkets reported a drop of 1.5% in sales volume over May, with a further 2.2% drop in specialist shops such as butchers and bakers.
Petrol and diesel sales rose by 1.1% in May, linked to people working back in offices as well as the increase in filling up a car.
One area not as badly hit, however, was clothing, with stores reporting a monthly increase in sales of 2.2%. Feedback to ONS suggested the increase was due to people buying new clothes for summer holidays.
Helen Dickinson, chief executive of the British Retail Consortium, said:
"Many customers are buying down, particularly with food, choosing value-range items where they might previously have bought premium goods."
Prices continue to rise overall, at their fastest rate for 40 years. UK inflation is currently at 9.1% - the highest level since 1982.
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