Meat, yoghurt and vegetables are among the items that have almost doubled in price compared with a year ago.
The new figures come as Downing Street prepares for a summit with food, farming and supermarket bosses later today.
Which? analysis of more than 26,000 products at Aldi, Asda, Lidl, Morrisons, Ocado, Sainsbury's, Tesco and Waitrose found that the prices of juice, chocolate, water, fish, chilled ready meals and cheese have also continued to rise.
• Four brown onions at Morrisons rose from 65p to £1.24 - a 90.8% rise
• Lancashire Farm Natural Bio Yoghurt 1kg went from £1.18 to £2.18 - a rise of 85.3%
• Aberdoyle Dairies Natural Cottage Cheese 300g at Lidl rose from an average of 67p to £1.34 - up 100.9%
• A 260g of own-brand salmon tails went from £3 to £4.54 - a rise of 51.4%
Food inflation fell slightly - from 17.2% in March to 17.1% in April, according to the Which? food tracker - but with costs rising in many areas of life, people are continuing to struggle.
Rebecca Tobi, senior business and investor engagement manager at The Food Foundation, said: "We know that the current food price crisis is causing a great many households to cut back on essentials.
"With levels of food poverty among children having doubled in the year to January 2023, government and businesses must act urgently to ensure that everyone can afford and access healthy essentials like fruit and vegetables.
"If not, we will be seeing the long-term health and economic consequences of the cost of living crisis playing out for years to come."
Later today, Downing Street will host a Farm To Fork Summit, bringing together representatives from farming, food, retail and supermarkets to talk about supply chains, resilience and food inflation.
Sue Davies, Which? head of food policy, said Prime Minister Rishi Sunak should ask supermarket bosses to "commit to do much more" such as stocking budget lines in convenience stores and providing transparent pricing so shoppers can easily find the best value items.
Ahead of the summit, Downing Street unveiled a package of measures that include greater protection for farmers in future trade deals.
It follows criticism of the recently announced trade deal with Australia, described by former environment secretary George Eustice as "giving away far too much for far too little in return".
Ministers have announced reviews into the horticulture and egg supply chains, following shortages of eggs and fresh produce on supermarket shelves in recent months - blamed on weather, Brexit and the conflict in Ukraine.
Other measures include reviewing supply chains to make sure producers are getting a fair deal and making it easier for them to turn some of their land into farm shops.
The horticulture sector has also been told that 45,000 visas will be available again next year (the same number as this year) to help them manage picking season.
Mr Sunak said: "I will always back British farmers, and I pay tribute to their hard work and dedication all year round which keeps shelves stocked and food on our tables.
"Supporting our farmers and food producers must, and always will be, at the heart of our plans to grow the economy and build a more prosperous country.
"That's why I'm proud to host this summit and, working together, I'm determined to build resilience, strengthen our food security and champion the best of British at home and overseas."