Researchers at Queen Mary University, London, found that while 80 bacteria lurk on each square inch of toilet, over 700 harmful bugs inhabit a car`s interior.
The study also found that 42 per cent of motorists regularly eat during driving, while only a third cleaned the inside of the car once a year and about 10 per cent said they never bothered to wipe down surfaces or vacuum.
"A car is the perfect place for germs to breed, especially if you eat in it and leave litter or uneaten food around," said lead researcher Dr Ron Cutler, director of biomedical science at the Queen Mary.
"To avoid potential health risks it would be wise to regularly clean your car inside and out," Dr Cutler was quoted as saying by the `Daily Mail`.
According to the researchers, the car boot was the filthiest area, with 1,000 bacteria for every one and half square inches.
They found that bacillus cereus -- a bug that can cause food poisoning and is found in rice, pasta and potatoes -- was the most common along with arthrobacter, which is found in soil and human skin.
Dr Cutler said: "While most of the bacteria were unlikely to cause health problems, some cars were found to play host to a number of potentially harmful bacterial species.
"Most people clean their homes but many are neglecting to clean their cars and are driving around in vehicles which resemble a rubbish bin."
The study, conducted for home store B&Q, also revealed that 66 per cent motorists did not check the oil and water levels before heading out on a long journey.