Men who keep a mobile in their pocket all day are four times more likely to suffer from infertility, an Israeli study has revealed.

The research - conducted at Haifa Technion and Carmel Medical Centre - also found that most men who speak on the phone for more than an hour a day see their sperm levels dropping to infertile levels.

Around 47 per cent of men who kept their mobile 50cm from their groin were found to have a “higher rate of abnormal sperm concentration,” according to Dr Ariel Zilberlicht, who led the study.

Of the men in the study who kept their phones further from their groins, only 11 per cent had a higher rate of abnormal sperm concentration.

Talking on your mobile for more than an hour - or using it while it charges - increased the chances of having an abnormal concentration of sperm to 61 per cent.

Male infertility constitutes between 30 and 40 per cent of all infertility cases.

Dr Zilberlicht told Israeli television station Channel 2: “In light of the results of the study, it is certainly recommended [that men] shorten the duration of calls and avoid carrying the device near their groins, sleeping next to it, speaking on it when it’s charging and use headphones or a headset as much as possible.”

The doctor also said that “men should turn their phones off while charging them.”

Researchers looking into the “association between characteristics of cell phone usage and semen quality” gave surveys to a sample of 106 men, who answered questions about their mobile phone usage.