Like so many of Man's best-laid plans, the Government's attempt to give children conceived from donated sperm the right to trace their biological father has gone astray.

When, in 2005, it became illegal to donate sperm anonymously, the Government and the Human Fertilisation and Embryology Authority assured would-be parents that this development would not shrink the supply of donor sperm. This has proved to be wrong.

While the number of donors has risen slightly, more men are donating only to women who are family or friends. In the first year of the new law, the number of women treated with sperm donated to sperm banks sank by a fifth. This is a dramatic statistic in arithmetical terms. In human terms it is frequently heartbreaking.

The case for ending the right of donors to retain anonymity may have been well intentioned, even if the new law was implemented before its full implications were explored. Yet by continuing to deny that a problem even exists in the supply of donated sperm, the Government is jeopardising the chances of finding a solution.

Existing donors can be spread only so far (inseminating a maximum of ten women, in order to avert any future risk of accidental incest). In the meantime, waiting lists for donated sperm lengthen. By the time some women decide to have a baby - only to discover that they cannot do so naturally - the waiting list is so long that their chances of conceiving at all are tiny.

Other women, keen to conceive, join the trail of “fertility tourists” to countries such as Denmark, where anonymous sperm donation is still legal. Others ask friends. Or they just give up.