Households are cutting back on food shopping as the rising cost of living bites into budgets.
Nearly half of adults surveyed by the Office for National Statistics (ONS) said they had bought less food in the past fortnight due to higher prices.
The price of food was also the most common reason for why those asked were seeing their monthly outgoings rising overall, the ONS said.
Supermarkets Asda and Tesco have said customers are cutting back on shopping.
Asda told the BBC that some shoppers are asking cashiers to stop scanning items when the till total hits £30 as they try to cut costs and also switching to budget ranges.
Meanwhile, Tesco, the UK's largest supermarket, has said it is seeing early signs that shoppers are changing their habits due to high inflation - the rate at which prices rise - such as buying less food and visiting more frequently.
The ONS said its feedback from supermarkets also suggested customers were spending less on their food shop because of the rising cost of living.
It found that sales in supermarkets dropped 1.5% in May, with a 2.2% fall in specialist shops such as butchers and bakers.
"Many customers are buying down, particularly with food, choosing value-range items where they might previously have bought premium goods," said Helen Dickinson, chief executive of the British Retail Consortium.
Retail sales overall fell by 0.5% in May, the ONS said, and it also revised down its sales growth figure for April to 0.4% from its previous estimate of 1.4%.
Prices overall are continuing to rise at their fastest rate for 40 years, with UK inflation at 9.1%, the highest level since March 1982.
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The RAC motoring group revealed that the average price of a litre of petrol hit £1.90 for the first time on Thursday, while diesel was edging towards £2 a litre.
Fuel and energy prices are the biggest drivers of inflation, but food costs drove the most recent rise in May, with prices for bread, cereal and meat climbing.
Sarah Coles, senior personal finance analyst at Hargreaves Lansdown, said the "horror" of April's unprecedented rise in energy bills "swallowed a much bigger slice" of households' income and "kept their appetite for spending under control".
"It's not just the rising bills of today that are worrying us, it's the prospect of even higher bills tomorrow, and fears of a looming recession, which might cause our finances to unravel entirely," she added.
Cutting back on food has emerged as the most tangible evidence of the effect of the soaring cost of living on our household finances.
This ONS report chimes with a survey commissioned by the BBC which found 56% of people asked had bought fewer groceries, and the same proportion had skipped meals.
The fact that it is food - a necessity for everyone, of course - shows how everyday life is affected, rather than just having fewer holidays or socialising less.
By the autumn and winter, the focus may well shift to people heating their homes less. But whether it is heating, eating, or both, people are going to be looking at where they can reduce their spending for some time yet.
In a BBC-commissioned survey of more than 4,000 people, 82% said they thought their wages should increase to match the rising price of goods and services.
Workers and unions have been pushing for pay rises, with strikes on the railways this week and BA workers at Heathrow voting to strike over the summer.
But the government has warned against employers handing out big increases in salaries over fears of a 1970s style "inflationary spiral" where firms hike wages and then pass the cost on to customers through even higher prices.
The drop in food sales comes as a long-running measure of consumer confidence recorded its lowest score since records began in 1974.
Market research firm GfK said its consumer morale index fell to -41 in June from -40 in May, below levels that have previously preceded recessions.
The ONS said that while food sales fell, fuel sales volumes rose by 1.1% in May - despite record high petrol prices.
Heather Bovill, deputy director for surveys and economic indicators at the ONS, said more workers returning to the office might be the reason in the uptick in fuel sales.
But she said the rise, along with boost in clothing sales, were "offset by falls for household goods and department stores, with retailers in these areas reporting consumer reluctance to spend due to affordability worries and higher prices."
The proportion of online sales slipped back in May but remains substantially higher than before the pandemic, the ONS said.
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