Data shows that tens of thousands of fresh supermarket chickens last year contained a potentially lethal food poisoning virus.
Waitrose was the worst offender, with up to one in 15 whole raw chickens carrying excessive amounts of campylobacter. This exceeded strict safety limits.
The retailer blamed factors “outside its control,” arguing that “unusually humid or foggy conditions” fueled the “unusually high” test results.
Campylobacter is the most common source of food poisoning. It usually causes diarrhea, nausea, and vomiting that improves naturally within a week.
However, in severe cases, it can endanger the lives of vulnerable groups, including young children, the elderly and immunocompromised.
It comes as five farms were stripped of their ‘RSPCA Assured’ status last month after an undercover investigation found chickens living in “appalling” conditions. Pictured is overcrowding at Harper Farm, where investigators witnessed cannibalism, neglect and intimidation.
Supermarkets must report figures on the prevalence of campylobacter among their poultry products every three months so that Food Standards Agency (FSA) officials can monitor food quality.
They share the proportion of their raw chickens that have more than 1,000 colony-forming units per gram (CFU/g) of Campylobacter.
At this level, chickens are considered contaminated and carry a higher risk of food poisoning.
Retailers are also supposed to ensure that no more than seven percent of their chickens exceed these levels.
The 2023 data, obtained by MailOnline, shows that 7.1 per cent of all Waitrose samples recorded between October and December had more than 1,000 colony-forming units per gram (CFU/g).
In comparison, the supermarket recorded rates of 4.04 percent between January and March and 2 percent from April to September.
In 2022, just 1.28 per cent of all Waitrose raw chicken tested contained more than 1,000 CFU/g.
While the chain acknowledged the rates were “unusually high,” it argued that “Campylobacter levels may be negatively influenced by seasonal changes and localized weather conditions.”
A spokesperson told MailOnline: “We are very confident that these isolated results based on a very small sample size do not reflect a trend that is working to understand this anomaly.”
Meanwhile, Lidl recorded the second highest rate overall in 2023, averaging 3.5 percent over the four quarters.
Morrisons, Marks and Spencer and Co-op all recorded average rates below two per cent in the time periods for which they shared data.
Tesco and Sainsbury’s stopped publishing data because they changed the way they monitor the pathogen in chicken, so their findings are not comparable with those of other retailers.
Aldi has not updated its related website or provided figures to MailOnline.
A Sainsbury’s spokesperson told MailOnline: ‘The safety of our products is extremely important to us and we have a variety of processes in place to monitor and limit campylobacter levels in our fresh chicken.
“We have consistently met the FSA target for Campylobacter levels for several years, so we will no longer be formally reporting on this.”
It comes as five farms were stripped of their ‘RSPCA Assured’ status last month after an undercover investigation found chickens living in “appalling” conditions.
Free-range egg farms in Leeds, Powys and Leicestershire supply major supermarkets across the UK, including Sainsbury’s.
Footage secretly filmed by the Animal Justice Project (AJP) revealed that tens of thousands of birds were living in dark, cramped sheds and were surrounded by the bodies and skeletons of dead chickens.
In some cases, the horrible conditions distressed the chickens, causing them to lose feathers and exhibit behaviors toward each other, including bullying, aggressive pecking, and even cannibalism.
Free-range egg farms in Leeds, Powys and Leicestershire supply major supermarkets across the UK, including Sainsbury’s. In the photo, chickens crammed inside one of the sheds on the Powys farm.
In some cases, the horrible conditions distressed the chickens, causing them to lose feathers and exhibit behaviors toward each other, including bullying, aggressive pecking, and even cannibalism. Pictured is a freezer full of dead chicken carcasses on the Powys farm.
Campylobacter is responsible for approximately 50,000 cases of illness in England each year and is one of the four leading causes of diarrhea in the world.
More worrying is the fact that some strains of the bacteria have mutated to develop resistance to antibiotics used by doctors to treat serious illnesses.
The latest statistics show that the average Brit consumes 35kg of poultry every year.
Apart from the misery and pain of the disease itself, the FSA estimates that the bacteria costs the economy around £900 million a year in terms of NHS treatment and days lost at work.
To avoid food poisoning, people should make sure they cook chicken thoroughly, separate the meat from other foods, store it in the refrigerator, and wash their hands and utensils after handling raw meat, according to the FSA.
Chicken should also not be washed because it can spread bacteria to other parts of the kitchen, he added.