If you are thinking about starting a family, you might want to begin by keeping your cell phone away from the family jewels:

Tests showed sperm counts plunged “significantly” in blokes who kept a phone in their trousers for just an hour a day – potentially preventing them from fathering children. Fertility consultant Professor Gedis Grudzinskas said: “Men need to think about their wellbeing and try to stop being addicted to their phones.”

Researchers monitored 106 men for a year and found 47 per cent of mobile phone addicts – four times higher than normal – had reduced sperm counts. Professor Martha Dirnfeld, of the Technion University in Haifa, Israel, said electromagnetic waves were effectively cooking sperm.

She said: “We analysed active sperm and found it had been reduced. We think this is being caused by heating from the phone and by electromagnetic activity.” Keeping phones close to the groin area, using them while on charge and even keeping handsets on a bedside table appears to lower sperm count.

Prof Grudzinskas, a Harley Street specialist and consultant at St George’s Hospital in London , added: “If you wear a suit to work put the mobile in your chest pocket. “And do you need to keep the phone on the bedside table? Some men keep their mobile in their shorts or pyjamas in bed. Is that really necessary?”

Not all experts agree with the sperm theory. Prof Alan Pacey, a fertility research scientist at Sheffield University, insisted he will continue putting his mobile in his pocket. But Prof Dirnfeld countered: “For younger guys it is a worry. If you are trying for a baby and it doesn’t happen within a year you might want to think of whether it could be your mobile phone habit that is to blame.”

And Graham Lamburn, of the Powerwatch research group, said the evidence of sperm reduction was “fairly compelling”.