In England, experts took swabs from the numeric keypads on a couple of ATMs and also took similar swabs from the seats of nearby public lavatories and compared the bacteria under microscopes in a lab.
It was found that the swabs from both the locations contained pseudomonads and bacillus, bacteria responsible for sickness and diarrhoea.
"We were surprised by our results because the ATM machines were shown to be heavily contaminated with bacteria to the same level as nearby public lavatories," the Telegraph quoted Richard Hastings, microbiologist for BioCote as saying.
"In addition the bacteria we detected on ATMs were similar to those from the toilet, which are well known as causes of common human illnesses," he said.
Previously, BioCote carried survey that revealed Brits consider public lavatories to be the biggest health risk.
The study of 3,000 adults also revealed public telephones are considered the biggest health risk.
Moreover, nearly than 42 per cent of Brits think the ATMs are dirty, with a quarter admitting they try not to use them to avoid having to touch the buttons, getting cash-back from shops instead.
Hastings said, "Public telephones can be a real hot spot for germs and grime."
"Not only are they handled by different people each day, but the handsets are then held close to people's nose and mouth."
"But it's ironic that while people perceive chip and pin pads to be the least dirtiest, our swabbing experiments have actually shown them to be dirtier than public lavatories," he added.