One in five households said that their monthly incomes would not stretch to cover all of their food costs in April and they had to use some form of borrowing such as a credit card, and overdraft or a loan or plunder their savings instead, consumer group Which? found.
This would equate to five million families if the findings were projected across the UK, Which? said. The findings provide an indication of the numbers of people who are struggling, despite official figures showing last week that personal insolvencies have fallen to their lowest level in five years.
The group who could not cover their food bills from their income alone was largely made up of low-income households earning less than £21,000 a year and squeezed 30 to 49-year-olds, many of whom had children.
Some 82% of these people said that they were worried about food prices and 57% were finding it "difficult to cope" on their current income. People in this group were also more likely to be worried about their level of debt and 74% of them described economy as "poor".
The study also found that only one quarter of people said that they were living comfortably on their incomes and more than one third (36%) felt squeezed.
Two-thirds are worried about the effects of low interest rates on their savings - although insolvency experts have credited low interest rates with helping people's borrowing costs and keeping personal insolvencies down.
Almost one third (31%) people surveyed cut back spending on essentials last month, and they were most likely to be women aged between 30 to 49 years old. More than two thirds (68%) of people across the survey described the state of the economy as poor, although 9% said it is good.
Around 2,000 people took part in the survey last month across the UK.