Eight out of 10 people wash their turkeys before cooking them, a survey finds - significantly increasing the risk of food poisoning.
Water alone cannot get rid of all germs
The Food Standards Agency (FSA) found women aged over 45 were the most likely offenders, with the North-East of England the worst black spot.
The FSA warns against washing meat because harmful bacteria can splash to worktops, dishes and utensils.
Germs that cause food poisoning can linger on surfaces for days.
On average, people eat Christmas dinner with six to seven other people
Men are more likely to carve, serve the drinks or relax while women are still the most likely to cook
About 58% of us buy fresh turkey, 26% buy a frozen one
This year we are likely to eat 15,000 tonnes of Brussels sprouts - equivalent in weight to 37 jumbo jets
Judith Hilton, head of Microbiological Safety at the Food Standards Agency, said: "Most people think they know how to prepare the Christmas meal with their eyes shut.
"But we've found that there are still a couple of Christmas food safety clangers served up each year. Turkey washing seems to be the most common blunder."
Ms Hilton said it was not possible to wash off all potential disease-causing agents from meat using water - the only way to kill them was to cook the meat thoroughly.
"By washing your raw turkey, you're actually more likely to spread the germs than get rid of them," she said.
Results from the survey show that 17% of people are not sure how to tell when their turkey is cooked.
Although formal reported incidents are fairly low, 2% of people think they have suffered from festive food poisoning in the past 5 years.
To ensure that turkey is cooked properly, make sure it is piping hot all the way through, cut into the thickest part to check that none of the meat is pink, and if juices run out they should be clear. The temperature should reach 70C for a least two minutes during the cooking process.
More than 2,000 people took part in the survey.