OPPOSITION to a ban on the reproductive cloning of human beings is based on two main types of argument. One defends individual "rights" to clone, the second scientific freedom. There is a fundamental flaw to the first approach: it claims the right for one person to predetermine the identity of another in the name of the individual freedom of the former.

This is based on an increasingly familiar argument, the "right to reproduce". First invoked in the name of infertile couples, it has been claimed by others barred by regulations on age, family circumstances and so forth from using available technology.

Claims that are couched in terms of competing and conflicting "rights" appear irreconcilable. Yet when the "right to reproduce" amounts to consumers' right of access to a product, it is not on the same level as the fundamental right to found a family stated in Article 16 of the Universal Declaration of Human Rights.

Article 16 defends a basic component of human life against political prohibitions, not the "right" to use any technology to overcome physiological impediments to natural reproduction. Whatever the commercial pressures or the compelling personal motives behind calls for cloning, they are not equivalent to the fundamental right of each new human being to a unique identity, The principle that each human life has equal intrinsic value transcending genetic, social or all other conditions hinges on the defining uniqueness of each individual. Cloning would remove the uniqueness that ensures no one has chosen and instrumentalised another person's identity. That uniqueness is the ultimate guarantee of human liberty.

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The argument for cloning in the name of scientific freedom is one that Unesco, the "intellectual arm" of the UN system, its International Bioethics Committee and I, as its director-general and as a biochemist, have examined very carefully.

First, a ban on the reproductive cloning of human beings does not close the door to the use of cloning techniques in embryology or the cloning of human tissue. These issues can and are being dealt with separately.

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More generally, the right to freedom of research is reinforced by the collective nature of a scientific community that shares a body of scientific knowledge and shares the rights and responsibilities that go with it.

The diminishing distinction between the science and the technology of genetics increasingly leads to claims to the same right to apply the technology as to conduct research. This carries risks for science as well as for society.

When the claim to freedom of research is misused to cover the use of controversial technology, valid claims to scientific freedom are undermined. Scientific freedom is also undermined when doubts about such a technique remain in scientific circles and in society yet scientists try to go ahead unilaterally.

An issue such as human reproductive cloning has to be dealt with collectively, involving both the scientific community and the community at large in ethical review and decision-making processes such as the one undertaken by Unesco.

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When scientists strive to tackle the ethical issues and to establish rules and guidelines, they actually reinforce and safeguard scientific freedom. They do so by winning the public trust required to underpin scientific freedom and by ensuring that protection of freedom of research is built into framework agreements.

This is the case with the Universal Declaration on the Human Genome and Human Rights, unanimously adopted by the 186 member states of Unesco, including Britain, last November. It proscribes the reproductive cloning of human beings because it is counter to the basic guiding principle of human genetics as set out in the declaration.

This is a balanced, collective response, following a four-year search by Unesco for the best possible expression of the deepest common values in all applications of human genetics.

When consensus is reached on the need to restrict certain new applications of science, critics charge that this is a hysterical, panic response. Such attacks appear increasingly anachronistic.

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Today the bioethical review process, a novelty only 15 years ago, has gained in depth and scope as it has gained experience. Scientific literacy among young people is rising. Today the potential of science to transform life as we know it is unprecedented.

For all these reasons, it is no longer credible to dismiss any restriction on scientific applications as retrograde and irrational. Knowledge is always positive but its applications can be negative or even perverse. We have entered an era of accountability where science can, and must, be consistent with human rights, where we apply science when it is feasible and acceptable.

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It is never neutral to let science and technology, rather than principles, determine what can be done, because it devalues the human factor. In the case of human genetics, what we mean by "human" must determine what we do with the genetics.

Federico Mayor is director-general of Unesco.