Contamination of fresh shop-bought chickens has risen significantly new figures released by the Food Standards Agency (FSA) show.
The FSA has also named individual retailers for the first time, showing Asda to have the highest number of chickens contaminated with campylobacter and Tesco the least.
The extent of food poisoning bug Campylobacter among shop-bought chickens will be revealed today.
The Food Standards Authority (FSA) will publish the second set of results, in the year-long testing of whole chickens bought from UK retailers and smaller independent stores and butchers.
The announcement will name individual retailers for the first time, following criticism of the FSA's decision not to identify retailers in the first set of results in August.
Campylobacter, which grows in the guts of chickens, is killed through cooking but is the most common cause of food poisoning in the UK with some 280,000 people affected every year.
Consumer groups say the presence of campylobacter's in so much supermarket chicken should shame Britain's biggest grocery chains.
Latest tests on fresh chicken being sold at major supermarkets show contamination of campylobacter has increased.