An expert has said that men should consider freezing their sperm to avoid their children suffering genetic disorders if they choose to have them later in life.

Studies suggest that sperm becomes more prone to errors with age, increasing the risk of autism, schizophrenia and other disorders, thus the need to freeze them as early as 18 years, experts say.

Furthermore, Dr Kevin Smith of Abertay University in Dundee believes freezing sperm on the NHS would avoid the risk of "gradually reducing human fitness in the long term".

In a paper in the Journal of Medical Ethics, Dr Smith said modern genetic studies had confirmed that the sperm of older men contained a greater number of mutations and that a minority of those mutations present a risk to the health of future children.

He added that "if demographic trends towards later fatherhood continue, this will likely lead to more children suffering from genetic disorders."

Furthermore, "a trend of later fatherhood will accelerate the accumulation of paternal-origin de novo mutations (genetic causes of disease) in the gene pool, gradually reducing human fitness in the long term.These risks suggest that paternal age is of ethical importance."

He said options to counter the risk include health education to promote earlier fatherhood and "incentives for young sperm donors and state-supported universal sperm banking".

Dr Smith said the issue of paternal age and its effect on the next generation of children should be taken seriously.

He said people in their 40s might want to use frozen sperm and that it should be banked ideally around the age of 18.

It costs an average of £150-200 per year to keep sperm privately.