Almost three quarters of fresh shop-bought chickens are contaminated with a food poisoning bug and almost a fifth have tested positive at the highest level, results show.

The Food Standards Agency's cumulative results from the first three quarters of its year-long survey of fresh chickens show the overall rate of contamination has increased to 73 per cent from 70 per cent in November and 59 per cent in August.

The proportion of chickens testing positive for the campylobacter bug above the highest level of contamination, or 1,000 colony forming units per gram (cfu/g), has risen from 18 per cent in November to 19 per cent, while seven per cent of packaging tested positive - up from six per cent in August.

Asda again sold the highest percentage of chickens contaminated with campylobacter at 78.9 per cent, with 31.1 per cent showing the bug above the highest level of contamination and 13 per cent of packaging testing positive.

Just over three quarters of chickens (76.2 per cent) sold by Morrisons tested positive, followed by The Co-operative (75.6 per cent), Marks & Spencer (75.2 per cent), Waitrose (71.7 per cent), Sainsbury's (69.6 per cent) and Tesco (68.2 per cent).

Individual figures for the discounters Aldi, Lidl and Iceland were not reported because their market share was based on 2010 figures and deemed too small, but the overall rate of campylobacter contamination among all retailers other than the major supermarkets was 76.9 per cent.

The FSA said none of the retailers were meeting the target for reducing campylobacter.

FSA director of policy Steve Wearne said: "We now know it is possible to make positive inroads in the reduction of campylobacter.

"Figures released today by M&S show that their intervention plan has resulted in fewer contaminated chickens on sale in their stores. If one retailer can achieve this campylobacter reduction through systematic interventions then others can, and should.

"Our survey is putting pressure on retailers to work with poultry processors to do more to tackle campylobacter. We want the industry to reduce the number of the most highly contaminated chickens as we know this will have the greatest impact on public health.

"Campylobacter is killed by thorough cooking, but it should not be left to consumers to manage the risk.

"It is the most common form of food poisoning in the UK, affecting an estimated 280,000 people a year. Poultry is the source of the majority of these cases, so the industry should be making every effort to ensure chickens are as free from campylobacter as possible before they reach customers."

MORE TOP STORIES:

Richard McDonald, chairman of the Acting on Campylobacter Together (ACT) board, said: "The UK is leading the way in the search for solutions to reduce campylobacter levels.

"We have learned a lot over the last five years about which interventions have the potential to make chicken safer. We must continue to work together to apply these successfully and help industry deliver the results we all want to see.”

He added: “Although the impact of industry interventions has not been seen in the results from the FSA survey to date, we look forward to seeing progress in the FSA's follow-up survey."

British Poultry Council (BPC) chief executive Andrew Large said: "We welcome the news that retailers and their suppliers are making significant progress, and hope that proven technology will be made commercially available across the sector.

"The BPC remains committed to collaborative working between industry, retailers and regulators, as we believe this is where long-term consistency will emerge. This joint effort is a complement to the creativity and investment we are seeing.”

Which? executive director Richard Lloyd said: " It's unacceptable that we're still seeing such high and rising levels of campylobacter in chicken.

"While four major supermarkets have made their action plans public - The Co-operative, M&S, Tesco and Waitrose - the remaining three have yet to say how they're planning to tackle this bug.

"People need reassurance that supermarkets are doing everything they can to make chicken safe. The remaining retailers must publish their plans and commit to action now before consumers lose confidence in them."