The British Fertility Society is warning that the country is facing a shortage of men willing to donate sperm.

Fertility clinics are struggling to recruit donors, have long waiting lists and high costs. In some parts of the country, there are no clinics at all.

The warning came Wednesday in the British Medical Journal from Mark Hamilton and Allan Pacey, members of the fertility society's board of directors.

They say part of the problem is that Britain banned anonymous sperm donation in 2005. Children who were born to a donor can now trace their biological parents once they are 18.

About 4,000 women a year in Britain need donor sperm to become pregnant. In 2006, only 307 men registered to become donors.