An online survey of 4,500 UK adults by the Food Standards Agency (FSA) found 44% washed chicken before cooking.
But it warns this spreads campylobacter bacteria onto hands, work surfaces, clothing and cooking equipment, through the splashing of water droplets.
Campylobacter affects about 280,000 people in the UK each year but only 28% in the FSA survey had heard of it.
Only a third of them knew that poultry was the main source of the bacteria.
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However 90% had heard of salmonella and E. coli.
The most commonly cited reasons for washing chicken were to remove dirt or germs, or because they had always done it.
Campylobacter is the most common form of food poisoning in the UK.
The majority of cases come from contaminated poultry.
Symptoms include diarrhoea, stomach pains and cramps, fever, and generally feeling unwell.
Most people are only ill for a few days, but it can lead to long-term health problems, including irritable bowel syndrome and Guillain-Barre syndrome, a serious condition of the nervous system.
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Chicken preparation advice
Cover and chill raw chicken
Store it at the bottom of the fridge to prevent juices dripping onto other foods
Don’t wash raw chicken
Thoroughly wash all utensils, chopping boards and surfaces used while preparing raw chicken
Cook chicken thoroughly – there should be no pink meat and juices should run clear
It can also kill. Those most at risk are children under five and older people.
FSA chief executive Catherine Brown said: “Although people tend to follow recommended practice when handling poultry, such as washing hands after touching raw chicken and making sure it is thoroughly cooked, our research has found that washing raw chicken is also common practice.