So Robert Winston plans to start genetically engineering human beings ("Fertile with ideas for the infertile", THES, May 14), despite previous claims that such possibilities are so far into the future they should not even be discussed. On the contrary, his current adventure testifies more than ever to the need for prophylactic democratic control over the direction of biological research.

The development of techniques for genetic engineering of humans is an issue in which society has a vital interest: it is not just for scientific entrepreneurs and their patients. In fact, there is no medical case for human genetic engineering.

The main advantage of HGE is said to be the elimination of disease genes from a family. Yet in nearly all cases, existing technologies such as prenatal and pre-implantation genetic testing allow the avoidance of genetic disease. There are only a few very rare cases where HGE is the only option for producing a healthy 100 per cent genetically related child. Couples certain to produce a genetically disabled child and who cannot, or do not want to deal with this, can choose not to have children, to adopt or to use donor eggs or sperm.

Given this, it is clear that the real market for HGE is in "enhancement" of appearance, height, athletic ability, intelligence and so on. As experience with drugs and surgery has shown, it would be impossible to prevent such uses once HGE were used for "medical" purposes. Such free-market eugenics would be a social disaster in many ways. Just one is that since access to such expensive technology would be on the basis of ability to pay, we could see the emergence of biologically as well as financially advantaged ruling elites. More subtle but with even more far-reaching social consequences would be the degradation of human subjects, entities with rights to be accepted as they are, into objects to be designed according to parents' whims.

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The consequences of such an ontological change for human dignity and for relationships between parents and children can scarcely be imagined. We cannot allow ourselves to be dragged into a new era of human history on the pretext of spurious medical benefits.

It is significant that Winston has chosen to start by engineering immature sperm cells. UK law prohibits only the genetic engineering of embryos. So Winston is doing nothing illegal. The government should remedy this and immediately sign and ratify the Council of Europe Convention on Biomedicine and Human Rights, which prohibits HGE.

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David King

The Campaign Against Human Genetic Engineering, London N16 Michael Antoniou

Guys Hospital Medical School Hilary Rose

Open University Chris Goodey

Institute of Education Angus Clarke

Institute of Medical Genetics University College of Wales