The debate that begins in the Commons on Monday on the Human Fertilisation and Embryology Bill is one of the most complex, controversial and important for years. The intensive lobbying, hyperbole and distortions that have preceded it are an indication as much of its crucial centrality to Britain's pioneering research in this field as they are of the emotions and moral dilemmas surrounding it. The Government has, throughout, acted with commendable common sense. It signalled its intentions some time ago, produced a discussion paper in 2006 and took good note of the subsequent views of experts. As a result, it has, in one important field, changed its mind, and will allow, rather than ban, research into embryos containing human and animal material. It has also rightly given MPs a free vote on issues that cut across religious, moral and political boundaries and where the public expects its legislators to decide matters in the interests of humanity rather than by the dictate of party whips.

The first of four debates will be on admixed embryos, known as “cytoplasmic hybrids” or “cybrids”. It is important to understand what is at issue. This is not the same as the therapeutic use of stem cells, though the two are linked. Nor is it the harvesting of cells from “saviour siblings” to help children with genetic diseases. It is altogether different from proposed legislation on the need for a father and on changing the time limits for abortion - and it is misleading and sometimes mischievous for opponents of the latter two issues to cite arguments, religious or moral, that are irrelevant to cybrid research.

This procedure uses an empty animal (usually cow) egg into which a human cell nucleus has been implanted, making it 99.9 per cent human. The aim is to use cells from people with genetic disorders to study the progressive development of diseases such as Parkinson's and test possible treatments. The culture can last for a maximum of 14 days and there is an absolute ban on the implantation into an animal or human womb. Such research, scientists hope, may eventually replace the need to test procedures on animals.

Opponents argue that the admixture of human and animal cells is not only inherently distasteful - “Frankenstein research”, as a leading cleric said - but takes science down a dangerous path that blurs the boundaries between human and animal life. Religious absolutists also attribute spiritual significance to an embryo, arguing that since it is the beginning of a sentient human being it must, necessarily, also be the embryo of a human soul. They say there is no proof that this research will yield findings of significance in fighting genetically based disease.

To this, scientists argue that without such research it is impossible to forecast what will or will not be useful. Their supporters should be careful, however, not to overstate their claims. Cybrids are not the only approach. But knowledge is so rudimentary that every avenue must be explored. For this reason it would be unwise to impose a complete ban, as is now proposed, on a related field, the creation of “true hybrids” that fertilise a human egg with animal sperm or vice versa. No research on this is presently contemplated. But no one knows what might later be possible or needed in this fast-moving field.

This newspaper stands squarely behind the advance of science. Governments cannot, and should not, seek to ban the investigation of nature. Scientific inquiry is a good cause in itself and the prerequisite to saving human lives - and souls - in the future. Advocates of science, though, must acknowledge that these advances are breeding ethical problems for the years ahead. How will we define what is “human” tissue? What if a human-animal combination could become self-sustaining? The result of banning this work will not be to prevent it happening but to drive it underground and overseas. The answer is not a moratorium but effective regulation. And in the Human Fertilisation and Embryology Authority, Britain has a highly effective way of taking into account the ethical, social, religious and scientific factors in all such research and ensuring a balance that commands public respect and scientific authority.