Households slashed their spending in supermarkets last month by £400million as many struggled to make ends meet.
Shoppers were also focusing on buying little but more often to help manage rocketing food bills, claims data specialists NielsenIQ.
These figures come on top of statistics from the Office for National Statistics that revealed food price inflation had jumped to more than 13%, the sharpest increase since 2008.
Key items such as cooking oil, milk and butter are rising even faster.
Cutbacks meant the amount paid in supermarkets fell to £12.1billion in the four weeks to September 10.
NielsenIQ also revealed budget chain Lidl was the fastest growing supermarket in the past 12 weeks.
A separate report last week said rival discounter Aldi had overtaken Morrisons to become the UK’s fourth biggest supermarket.
Mike Watkins, from NielsenIQ, said: “Some 57% of consumers are saying they have been severely or moderately affected by the cost-of-living crisis – and in three months this is anticipated to rise to 76%.
With inflation expected to remain close to current levels for the rest of the year, this will encourage households to shop around for savings.”
Online grocery sales have fallen by 7% in the past year as people do more of their shopping in store.
Further research shows half of adults are struggling with minimum monthly payments on credit cards.
That poll also found 57% reported using credit to make ends meet over the last year.
