Tesco is the least hygienic of Britain's big four supermarkets, with environmental health inspectors finding more serious problems at its premises than at Asda, Sainsbury's and Morrisons, according to a league table of checks by local authorities.
In a five-star rating system, 5 per cent of Tesco stores scored less than the three-star rating which indicates good compliance with health laws, according to statistics passed to The Independent.
At Asda, the figure was 4 per cent, at Sainsbury's 3 per cent – and Morrisons none – indicating that as many as 150 big stores owned by the three largest grocery chains breach food safety legislation.
The results provide unwelcome publicity for Tesco, Britain's biggest retailer with a 28 per cent market share, following several allegations of rodent infestations and other breaches of food safety laws at its stores during the past year.
The hygiene survey was published amid plans by the Government's food watchdog, the Food Standards Agency (FSA), to relax the scoring system for food businesses. At present 214 of the 325 local authorities in England rate restaurants, cafes, pubs and shops using a five-star system.
Of these, 98 supply a summary to scoresonthedoors.org.uk, a website run by a company called Transparency Data, which checked the ratings of 1,715 stores operated by Tesco, Asda, Sainsbury's, Morrisons, the Co-op, Marks & Spencer and Waitrose. Of 490 Tesco outlets, 20 were two stars, seven were one star and two merited no stars at all, suggesting that one in 20 Tesco food outlets was falling foul of the law in some way.
Outside the Big Four, 9 per cent of the 431 outlets operated by the fifth-largest supermarket, the Co-op, scored less than three stars. Waitrose had the best record, with all its outlets either five or four stars, just ahead of Marks & Spencer, which had 97 per cent of stores in the top two bands.
However, there were marked differences between retailers with similar customer demographics; while Tesco had five per cent rated zero to two stars, all of Morrisons' premises were rated three stars or more.
To compile their reports, health officers checked aisles, bakeries, fishmongers, public cafés, petrol stations shops and staff canteens.
According to the scheme, two-star premises must make more effort to meet food safety legislation. Outlets with one star are "very poor: little or no appreciation of food safety. Major effort required".
According to the Health Protection Agency, about 4.5 million people in England and Wales suffer food-borne illnesses such as salmonella and E. coli annually from food consumed in the home and restaurants. Although many supermarket items are packaged in tins and plastic, others such as fresh bread, fish and sandwiches, are more vulnerable to dirt and infection.
During the past year, Tesco, which has annual sales of £60bn, has run into trouble with environmental health officers on several occasions:
*Last September, 24 products were past their sell-by date at a Tesco store in Llandudno, including one item 12 days past its expiry date
*Last October magistrates in Cardiff fined Tesco £6,000 for selling a chocolate cake gnawed by rats
*In April, environmental health officers linked three suspected cases of food poisoning to fresh tuna from Tesco in Inverness
*In May, Suffolk Coastal District Council accused Tesco's Martlesham store of being "heavily" infested with mice. Tesco denies eight charges brought by the council in an ongoing case.
*Last month, Tesco had to close its staff canteen at Inverness for a week because of a cockroach infestation.
In a statement, Tesco said it took hygiene standards extremely seriously. "It is widely recognised that the majority of the existing local 'scoring schemes' are subjective and inconsistent with ambiguous methodology leading to misinterpreted findings and misleading results – this being a case in point," Tesco said.
"For example, the measures are not balanced, as in some cases whole stores are rated and in others each area of the store gets a separate score. To address this the FSA is proposing a new national scheme that will introduce a more credible and reliant system."
The Co-op also said it took food safety and hygiene extremely seriously. "The Co-operative has the second-highest number of five, four and three-star ratings – by a considerable margin."
Food safety campaigners had hoped a unified national system would drive up food safety through compulsory display of ratings on the premises, hopefully "above the doors". However, after studying the issue for two years, the FSA proposed last week to widen the top grades, meaning fewer food outlets would fail inspections without any improvement in performance. Supermarkets are believed to have strongly pressed for the measure.
Out of the 1,750 stores in the survey, none would receive a no-star rating and only three – from the Co-op – would have received a one-star rating, according to Paul Hiscoe, a director of Transparency Data.
He said: "The existing scheme is already running in over two-thirds of councils in England and works well. However, a couple of the largest supermarkets are worried about their reputations being damaged by anything less than five stars and appear to have persuaded the FSA to water down the requirements to achieve the very top ratings."