Over two thirds of fresh chickens sold in the UK have been found to contain the campylobacter bug, the Food Standards Agency (FSA) has found.

Research by the FSA shows that 70% of chickens tested showed evidence of the bug, which can cause food poisoning and even death if the meat it lives on is not cooked thoroughly.

The FSA said that of the major supermarkets Asda’s chickens showed the most incidents of campylobacter, followed by Marks & Spencer.

Of the chickens tested, 28% of Asda’s were found to be contaminated, defined as having more than 1,000 colony-forming units per gram. M&S was the second highest, with 22% of its chickens over that level.

With a contamination rate of 11% Tesco was the best-performing of all the big four.

The research was carried out on just under 2,000 fresh chickens sold in supermarkets and grocers around the UK.

FSA director of policy Steve Wearne said: “These results show that the food industry, especially retailers, need to do more to reduce the amount of campylobacter on fresh chickens.”