Cooking the meat properly kills the bug
Two-thirds of chicken on sale in the UK is contaminated with a bacterium which can cause severe food poisoning, research shows.
Campylobacter, which can cause diarrhoea, cramping and abdominal pain, causes 55,000 cases of food poisoning a year in the UK.
However, cooking the meat properly kills the bug.
The Food Standards Agency, which carried out the research, said the poultry industry should take action.
It said levels of campylobacter in chicken were the same as when a similar survey was last carried out in 2001.
However, the latest survey did find that levels of another common cause of food poisoning - salmonella - had fallen, with just 6% of samples showing traces of the bacterium.
Illness caused by campylobacter infection usually clears up after a week.
But there is evidence to suggest that it can trigger a life-threatening bloodstream infection in people with a weakened immune system.
Andrew Wadge, FSA director of food safety, said the poultry industry should take action to try to reduce levels of campylobacter infection.
There is no effective way to prevent campylobacter spreading between flocks.
But countries such as New Zealand and Denmark have successfully reduced infection rates through measures such as minimising contact between birds at slaughter.
However, the campylobacter infection rate among chickens reared in the UK was 76%.
Mr Wadge said: "The continuing low levels of salmonella are encouraging, but it is disappointing that the levels of campylobacter remain high.
"It is obvious more needs to be done to get these levels down and we need to continue working with poultry producers and retailers to make this happen."
Ted Wright, chairman of the British Poultry Council, said the results of the latest survey were not comparable with previous research as the method used to collect information was different.
He said scientific knowledge about campylobacter - including how to measure its presence - was incomplete.
However, he said: "We need to concentrate on finding effective measures to prevent infection in flocks."
Campylobacter is the most common bacterial cause of food poisoning, according to the FSA.
As well as chicken it can be found on other meat, unpasteurised milk, and untreated water.
To ensure that cooking has killed the bug, the bird should be cooked until the juices from it run clear.
The FSA tested 3,274 samples of fresh chicken at retail across the UK between May 2007 and September 2008 for the presence of campylobacter and salmonella.
The agency set a target in 2005 to deliver a 50% reduction in the prevalence of campylobacter in UK produced chicken on sale in retail outlets by 2010.
Campylobacter prevalence in poultry flocks varies with the seasons, with a pronounced summer peak.