Retailers have been accused of increasing retail prices but failing to share the proceeds with vegetable growers hit by heavy costs. The UK retail price of vegetables has risen significantly in the past year, with potatoes up 25.2%, carrots up 18.3% and onions up 16.7% according to figures from The Grocer 33 price survey. But farmer Fraser Key of Key’s of Lincolnshire – who said he felt he now had nothing left to lose by speaking out – claimed retailers had mostly pocketed the increases.

“The retail prices are well up on last year, but none of that money has been passed to the grower and only some to the packers. Retailers are making a fortune while growers are crucified. Class one onions sell for 85p per kilo. The grower can get as little as 8p per kilo, while a packer might only get 30p per kilo for packed, delivered produce,” he said. “People won’t speak out about what’s happening because they’re afraid their business will vanish.”

One major supplier claimed retailers were keeping margin on fruit and veg to build a war chest for their price battle elsewhere. And the National Farmers Union (NFU) said retailers had been warned growers needed more money, but hadn’t responded.

“Input costs have soared. I’m paying 150% more in fertiliser costs, and land rents are up,” said Richard Hirst, chair of the NFU board for horticulture and potatoes. “It’s disappointing retailers have maintained prices at high levels and yet our margins haven’t seen this. Within current retail prices there are opportunities for the growers to receive more.”

A spokeswoman for Asda said: “We are confident our suppliers have a strong relationship with their growers, ensuring they have sustainable and profitable businesses. We trade through our supply base, not directly to growers, and trust them to pass these costs back to the farmers.”

Sainsbury's said it would investigate if details of the suppliers were provided. Tesco and Morrisons declined to comment.