The figure rises to 40 percent of over-60s living in a household with a maximum £20,000 income – at least 1.8 million homes.
Age UK is now calling on the Government to urgently extend targeted support for less affluent pensioners already facing higher energy bills this year.
The charity said that with colder months looming, there is a significant risk many pensioners will see their food budgets as the only flexible outgoing that can be shrunk to balance the books, putting their health at risk.
Its survey of more than 1,200 over-60s shows 39 percent are worried they will not be able to afford enough food or quality items as a result of soaring energy prices.
Alarmingly, the analysis also reveals that pensioners are spending far more of their money on higher supermarket prices.
Today a typical pensioner household spends about £50 per week on food and non-alcoholic beverages, which represents 16.4 percent of their after-tax income.
But this was just £38 (13.7 percent in 2021. This means that since the cost-of-living crisis, they are spending £640 extra a year on food.
Caroline Abrahams, the charity director at Age UK, said: “It’s really worrying to discover from our research that so many older people are already cutting back on their food shopping.
“Once it gets colder their costs will substantially rise, so what will they do then?
“We fear the answer is that many will feel they have no choice but to ration their food and other groceries, potentially putting their health at risk.”
She went on: “Malnutrition has long been a real problem for many older people.
“Loneliness, social isolation, disability and common health problems can all impact on older people’s appetite or ability to eat, access or prepare food.
“Typically, lack of funds was not the major factor, but sadly the picture is changing.
“Poverty is now clearly playing a much bigger part in some older people going without the nourishment they need.”
The past 12 months have taken their toll, as a recent YouGov poll found that 36 percent of people aged 65 or over in Britain would describe their financial situation as being worse than a year ago.
A further 14 percent reported that it continues to be as bad as last year – although 34 percent of those eligible for Pension Credit are still missing out on the key benefit.
In the latest year for which data is available, 2019 to 2020, some £2.4billion of Pension Credit and Housing Benefit went unclaimed by Britain’s older people.
