The Ohio study sampled 364 men treated with their partners at fertility clinics in Mumbai, India. The results were reported to the American Society for Reproductive Medicine in New Orleans.

The team found that heavy users who were on their phones for more than four hours a day had the least average sperm counts, at 50 million per milliliter, and the least healthy sperm.

While men who reported two to four hours a day use had average sperm counts of 69 million per ml and with regular healthy sperm.

The men who said they did not use mobile phones at all reported the highest average sperm counts of 86 million per ml, along with the highest quality sperm.

Lead researcher, Dr. Ashok Agarwal, said the study did not conclude that mobile phones affected fertility, but proves that more research needs to be done.

He said: "There was a significant decrease in the most important measures of sperm health and that should definitely be reflected in a decrease in fertility, which is seen worldwide."

"People use mobile phones without thinking twice what the consequences might be."

"It is just like using a toothbrush, but mobiles could be having a devastating effect on fertility."

"It still has to be proved, but it could be having a huge impact because mobiles are so much part of lives."

He said that the radiation emitted by mobile phones could have adverse effects on the sperm by affecting DNA.