Fertility experts are warning man that using a mobile for as little as an hour a day is "cooking sperm" and lowering level significantly. The new study shows that having a mobile phone close to the testicles - or within a foot or two of the body - can lower sperm levels so much that conceiving could be difficult.
The findings have led to a leading British fertility expert to advise men to stop being addicted to mobile phones.
"If you wear a suit to work put the mobile in your chest pocket instead of close to your testes. It will reduce the risk of your sperm count dropping or dropping so much."
The study - by highly respected specialists - found that sperm levels of men who kept their phones in their pocket during the day were seriously affected in 47 per cent of cases compare to just 11 per cent in the general population.
Professor Martha Dirnfeld, of the Technion University in Haifa, said: "We analysed the amount of active swimming sperm and the quality and found that it had been reduced.
"We think this is being caused by a heating of the sperm from the phone and by electromagnetic activity."
The team monitored more than 100 men attending a fertility clinic for a year.
The quality of sperm among men in Western countries is constantly decreasing, they found. They also found that besides men keeping their phones close to their groin many spoke on the phone while it was charging and kept it only a few centimetres from their bed.
Even keeping the phone on a bedside table appears to raise lower sperm cell counts.
They also discovered the quality of sperm among men in Western countries is constantly decreasing and is considered crucial in 40 percent of the cases in which couples have difficulty conceiving a child.