Which? found one particular item - a six-pack of Mr Kipling Chocolate Slices - rose by 129% at Tesco, the single largest price increase year on year.

The average cost of the pack went up by £1.50 in the 12 months to July 2023.

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Six of the same brand's bakewell slices at Sainsbury's came in at £2.75, up by 99%.

The heftiest price hike at Asda was on a kilo of Lancashire Farm Natural Yogurt and the same brand's fat free option which rose 80% from £1 to £1.80.

At Morrisons, two packs of Pilgrims Choice cheeses went up more than 75% to £2.11.

To help struggling shoppers, Which? is calling on major retailers to make sure they stock budget range alternatives in smaller stores and has said it will monitor their progress.

The consumer group analysed the prices of almost 26,000 food and drink products for its food inflation tracker at eight major supermarkets - Aldi, Asda, Lidl, Morrisons, Ocado, Sainsbury's, Tesco and Waitrose - to see how individual product prices are being affected.

It isn't all bad news, though, as overall, supermarket food inflation fell by more than 1.5% for the month to the end of June, helped by cuts in the prices of, for example, milk and butter, in recent months.

But, in both cases, prices at the tills are still significantly higher compared to what shoppers were paying before the cost of living crisis began.

Sue Davies, Which? Head of Food Policy, said: "The scale of price hikes to some branded products at the supermarket over the last 12 months is barely believable and highlights the huge pressure faced by shoppers, especially families and those on low incomes.

"With food prices expected to remain high for the rest of the year, Which? is calling on supermarkets to ensure expensive convenience stores are stocked with a range of budget items that support a healthy diet."