Mobile phones have 18 times more bacteria than toilet flush handles.
According the consumer group, Which, mobile phones can harbour 18 times more living bacteria than the flush handle on a men's toilet.
A hygiene expert who swabbed and analysed 30 handsets for the study found seven had warning or high levels of environmental bacteria.
The tests showed how easily bacteria could linger on the surface of a phone, which could be passed on to other people if they held the handset to look at photos or other applications.
The results of the 2007 study carried out in Britain also found that there were more germs on mobiles than the average door handle, keyboard or bottom of a shoe, or even a toilet seat.