A SPERM shortage is affecting fertility clinics since a change in the law removing the right to anonymity for donors.

The number of sperm donors has declined rapidly since 2000, due to growing awareness that men could be contacted by children born from their donation.

The fall in numbers was discovered by North-East researchers.

It has led to a plea by the Newcastle Fertility Centre for more men aged under 40 to volunteer.

The number of donors is dwindling to double figures, with only 25 offering their sperm in 2003.

A survey of 1,100 potential donors between 1994 to 2003 revealed that 88 per cent of applicants were under 36, more than half were students without a partner, 85 per cent were unmarried and more than three quarters had no children.

The results are published today in the Human Reproduction journal.

After screening, only four in every hundred sperm samples were deemed as suitable.

Overall, there is downward trend in the annual number of applicants from about 175 in 1994 to about 25 in 2003, with the sharpest fall occurring from 2000 onwards.

From 1999, the numbers who changed their mind during the process increased.

Former Newcastle Fertility Centre expert Dr Sudipta Paul, who is now at Whitehaven Hospital, in Cumbria, said the study showed that the number of men interested in donating sperm had declined significantly.

This fall could continue due to the removal of anonymity for men recruited since April this year.

Demand for donor sperm is likely to increase because of a predicted decline in the semen quality in the UK.

The potential gap between supply and demand has led Dr Jane Stewart, honorary lecturer with Newcastle University, to call for a change of tactics in recruiting donors.

"It is difficult and costly to recruit sperm donors.

"With the change in the anonymity rules, we saw a sharp fall in numbers and a change in the profile of the applicants, perhaps reflecting the attitudes of different groups to anonymity.

"There was a significant increase in the number of men who had partners and, after the Department of Health announcement that anonymity would be removed, there was a substantial fall in the numbers of students," said Dr Stewart.

Men wishing to become donors should contact their local fertility centre.