One in six mobile phones in Britain is contaminated with faecal matter, according to new research.
Experts said the most likely reason for the potentially harmful bacteria festering on so many gadgets was people failing to wash their hands properly with soap after going to the toilet.
The findings of the UK-wide study by scientists from the London School of Hygiene & Tropical Medicine and Queen Mary, University of London also revealed a tendency among Britons to lie about their hygiene habits.
Although 95% of people said they washed their hands with soap where possible, 92% of phones and 82% of hands had bacteria on them. Worryingly, 16% of hands and 16% of phones were found to harbour E.coli - bacteria of a faecal origin.
Harmful E.coli (Escherichia coli) is associated with stomach upsets and has been implicated in serious cases of food poisoning such as the fatal O157 outbreak in Germany in June.
Dr Val Curtis, from the London School of Hygiene & Tropical Medicine, said: "This study provides more evidence that some people still don't wash their hands properly, especially after going to the toilet.
"I hope the thought of having E.coli on their hands and phones encourages them to take more care in the bathroom - washing your hands with soap is such a simple thing to do but there is no doubt it saves lives."
The findings were released ahead of the annual Global Handwashing Day on Saturday.
In developed countries, hand washing with soap helps to prevent the spread of viral infections, such as norovirus, rotavirus and influenza.
Global Handwashing Day - which is held on October 15 every year - aims to transform the action of washing hands with soap into an automatic behaviour, deeply set in our daily lives.