SOME of Britain’s biggest supermarket chains are compromising on quality by selling budget items such as sausage rolls with as little as 6% pork.

Sainsbury’s and Tesco are working hard to market their low-cost lines as they compete with discount chains to attract cash-strapped shoppers.

This is often coming at the expense of quality, however. An analysis of low-cost foods at the two chains has found, in addition to the sausage rolls, fisherman’s pies with 9% fish and square cheese slices with 11% cheese. The products have been bulked out with ingredients such as water, animal fat and sugar.

The items help the supermarkets to undercut bargain-basement stores such as Aldi and Lidl, which have posed a growing threat as middle-class families seek to economise.

In many cases the German-owned discount chains also have higher-quality food than the bigger chains.

Professor Tom Sanders, head of nutritional sciences at King’s College London, said: “This is cheap, second-rate food ingredients masquerading as real food. They are heavily processed foods using added fat, water and sugar. People tempted by the low prices should look carefully at the labels.”

At Sainsbury’s, the Basics range is now a vital plank in the supermarket’s strategy. Justin King, chief executive of Sainsbury’s, said earlier this month that a 25% increase in sales of Basics products had boosted half-year profits to £272m.

He was less expansive, however, about the quality of the budget range. Four chicken and vegetable pies, for example, cost 84p but contain only 9% chicken and 2% vegetables.

The back of the packet shows that there are 44 ingredients. The main ones are wheat flour, water and margarine along with additives such as maize starch, emulsifiers, glucose syrup and colourings.

Sainsbury’s chocolate mousse costs 28p but contains only 2% chocolate. The main ingredients are milk, sugar and cream. The main ingredient in Basics tinned curry, at 48p, is water; chicken is 12%.

At Tesco, the Value range is almost identical in terms of price and ingredients. Both supermarkets sell processed cheese slices that cost 51p but contain only 11% cheese. The main ingredient is whey powder, a byproduct of cheese making, followed by vegetable oil, milk proteins and emulsifying salts.

At Tesco, a 700g pack of frozen sausage rolls costs 65p but contains 6% pork. The main ingredient is water followed by wheat flour and vegetable oil, with added pork fat, salt and emulsifiers.

The Tesco Value 300g fisherman’s pie is 75p, almost £2 cheaper than the standard 500g fish pie, but contains almost two thirds less fish at just 9%. The main ingredients are mashed potato and water with added fish stock and gelling agents such as pectin. A tin of Tesco Value chicken curry costs 48p but is only 12% chicken.

Tim Lang, professor of food policy at City University, said: “It’s about consumer expectations. You would expect a fisherman’s pie, for example, to be mostly fish. If it contains mostly potato with 9% fish then it should be called potato pie with a bit of fish.”

The Basic and Value budget ranges are cheaper than food in the discount stores. But Aldi and Lidl’s food is often cheaper than the standard ranges in Tesco and Sainsbury’s – and a second survey found that it was often better quality, too.

Sainsbury’s own brand marmalade, for example, costs 75p and has 26g fruit per 100g. At Lidl, however, the orange marmalade has 5% more fruit and costs 55p.

In Tesco, 500g of pasta sauce contains 56% tomato and 9% puree and costs 79p. In Lidl, a similar jar of pasta sauce costs 67p and contains 72% tomato.

Tesco’s bramley apple pies cost 69p and have 15% apple. Aldi’s Holly Lane bramley apple pies cost the same amount but contain 45% apple.

Sainsbury’s wafer-thin cooked ham costs £2.38 for 400g while 450g of Tesco wafer-thin honey-roast ham costs £2.98. Both contain 80% pork. At Lidl, by contrast, 400g of wafer-thin ham contains 97% pork and costs £2.19.

Tesco and Sainsbury’s cream of tomato soup both cost 39p and contain 68% and 74% tomato puree respectively. Aldi tomato soup costs 37p but contains 91% tomato puree.

Sarah Dennis, a senior researcher at Which?, the consumer group, said: “The snobbery value has gone from it. People are more aware you can get just as good if not better products at the discount retailers.”

Claudine Spiteri, a 30-year-old mother, lives in east London and runs a corporate entertainment company called Livestock Productions. She discovered Lidl two years ago and now prefers shopping there to her local Waitrose and Tesco.

She said: “They’ve got a great range of continental food and I find the quality of the meat is better.”

Sarah Finn, a 45-year-old mother and church employee from east London, shops in Lidl for her fruit and vegetables and goes to Sainsbury’s and Tesco for luxury items.

She said: “I noticed that the fruits and vegetables last longer and Lidl have good offers. I still haven’t tried their tins yet, though - I’m still unsure about those.”

A spokeswoman for Sainsbury’s said that its meat was ethically sourced and of high quality. She said: “Product integrity is at the heart of all our ranges - from premium to value - thereby offering customers the highest quality food at fair prices.”

Tesco said it had recently started discounting branded items to compete with Aldi and Lidl on price and content.

Additional reporting: Kevin Dowling and Kaitlin Meehan

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