Food prices jumped at the fastest rate since 2008 in August - climbing 9.3% year-on-year - following a 7% hike last month, according to the British Retail Consortium (BRC) and NielsenIQ index.
They attributed the surging prices to Russia's invasion of Ukraine, which impacted supplies of fertiliser, vegetable oils, wheat and animal feed.
Mike Watkins, head of retail and business insight at NielsenIQ, commented: "Inflation continues to accelerate and shoppers are already cautious about how much they spend on groceries, with a fall in volume sales at supermarkets in recent months.
"We can expect this level of food inflation to be with us for at least another six months but hopefully some of the input cost pressures in the supply chain will eventually start to ease.
"However, with further falls in disposable incomes coming this autumn as energy costs rocket again, retail spend will come under pressure in the all-important final quarter of the year."
Fresh food prices rose 10.5% this month, with milk and margarine experiencing the largest increases.
Shop price annual inflation, meanwhile, climbed to 5.1% - the highest since the BRC index began in 2005.
Helen Dickinson, BRC chief executive, insisted the outlook was "bleak for both consumers and retailers", but believes businesses would help via "discounts to vulnerable groups, expanding value ranges, fixing prices of essentials and raising staff pay".
She called for support for businesses from the next prime minister, who will be the winner of the Conservative Party leadership contest, Liz Truss or Rishi Sunak.
"The new prime minister will have an opportunity to relieve some of the cost burden bearing down on retailers, like the upcoming increase in business rates, in order to help retailers do more to help their customers," Dickinson commented.