MEN who wear kilts have better quality sperm and are therefore more fertile, Scottish researchers claim.

They say that wearing a kilt traditionally – without underpants – could provide the ideal environment for sperm.

For testicles to produce adequate levels of sperm, they need to be three degrees Celsius lower than body temperature.

But recent research has shown there has been a global decline in the quality of men's semen over the past 50 years.

In addition to this, there has been a decline in fertility rates across the industrialised world.

Although the reasons for this are many and complex, it is thought that a reduction in sperm quality has played a role.

It is not fully understood why sperm quality is deteriorating but changes in lifestyle and increased pollution have been suggested as possible factors.

But, the new research, published in the Scottish Medical Journal, could provide men with a solution to their poor quality sperm. It said that since the 1980s scientists have linked tight-fitting underwear to impaired male fertility.

This was proven in 1990 when experts found tight pants increased the temperature deep inside the testicles.

Experts say that tight-fitting pants are partly responsible for declining fertility.

On average, tight undergarments increased the temperature of the air surrounding the testicles by 3.5 degrees celsius.

Dr Erwin Kompanje, who wrote the review, said a recent study found that there are even more serious effects of not airing a man's groin. Not only did it slow production, but it caused the testicles to produce substandard sperm which could not swim to fertilise the egg.

The study said: "It seems plausible that men should wear skirts and avoid trousers, at least during the period during which they plan to conceive."

The study added that wearing a kilt provides strong psychological benefits to men too as "it will get you noticed no matter where you are".

Ellen Thomas