Tang Lixin , a Guangzhou doctor working at one of the few sperm banks on the mainland, said yesterday that most of the country's sperm donors were college students who were paid for their efforts. 'We hope to see more healthy men, married or not, become semen donors and help infertile couples,' he said.

'The soaring demand is draining our deposits. Other sperm banks on the mainland are having the same problem.'

The Guangzhou Sperm Bank, one of five authorised by the Ministry of Health nationwide, has only signed up 700 donors since its establishment early last year.

Married couples have been seeking help at the rate of more than 50 a month. 'Some of these couples have come from Hong Kong and Taiwan,' Dr Tang said.

'Couples anxious to have children are having to wait in line for appropriate semen.'

Dr Tang said mainland health authorities had ruled that the services would only be available to Chinese people.

The Guangzhou operation also offers a service allowing men to deposit sperm for future personal use should they become infertile.

At the sperm bank in Nanjing , nearly 90 per cent of the donors are college students, who receive about 1,000 yuan for eight donations - the usual amount needed for successful fertilisation.

However, doctors said medical check-ups had found that more than half the donors had poor-quality semen, which was rejected to prevent the possibility of babies being born with health problems.

To regulate the 'assisted reproduction market' in China, the Ministry of Health introduced a licensing system in August 2001, with only a handful of sperm banks in Beijing, Shanghai, Nanjing, Guangzhou and Changsha , in Hunan province , getting the go-ahead.

Before licensing was introduced, there were 44 sperm banks in China, with more than 500 hospitals performing artificial insemination.

Medical experts had warned that ethical problems could arise in an unregulated market.

'Now, semen from one donor can only be supplied to five women at most, and the donor is also not allowed to make donations at a second sperm bank,' said Dr Tang.

Mainland media has reported the establishment of an elite sperm bank in Chengdu , Sichuan province , with donors either having academic degrees equal to associate professor or above, being sports or entertainment stars, or senior managers or bankers.

The elite sperm bank has come under fire from sociologists and others.

'Our aim is to help sterile couples have healthy babies, not super babies,' said Dr Tang.