Layla Jader, a public health consultant from Wales, said viewers watch chefs serve up salads without washing the ingredients and often forget to wash their own hands.
Chopping different ingredients with the correct boards and knives was also vital to reduce the chances of food poisoning, she said.
Layla Jader said if viewers followed their example they would be at risk of food poisoning bugs like salmonella and E.coli.
Programmes like 'Ready Steady Cook', hosted by Ainsley Harriott, and 'Celebrity MasterChef' were among the worst culprits.
Jader called for a campaign to remind people of the need to get "back to basics".
She said health inspectors should check standards in restaurant toilets as well as kitchens and parents should teach the importance of regular hand washing to children.
"I really get frustrated, I've seen it so many times. They bring in the vegetables, they open the bag and they make the salad straight from unwashed vegetables," the Telegraph quoted her, as saying.
"They do it for the sake of expedience but these programmes are watched by millions of people.
"It's irresponsible. If they are going to do something that's not healthy they should say: 'We are in a hurry but please wash the salad and vegetables before you serve it'.
"In Ready Steady Cook they cut the salad from the windowsill. They also get the bag and open it on the table. I think we have to remember there are impressionable young people watching," she added.
Meat is often particularly heavily contaminated with bugs, she said, but these are often killed during cooking. But chefs must take care not to use the same utensils on salad or vegetables that are going to be eaten raw.