If Christians really believe that embryos are morally equivalent to living, breathing humans, they would stop trying for children. It has been estimated that for every live birth resulting from sexual intercourse at least three embryos are naturally wasted, which makes all Christian parents, according to their own principles, murderers.

But this rather striking fact has neither registered with the Christian lobby nor deterred it from seeking to impose its dangerously incoherent convictions on the rest of us. As the Human Fertilisation and Embryology (HFE) Bill comes before the Commons today, some churchgoers continue to crusade for a ban on potentially groundbreaking research on embryos. Why? Because these microscopic bundles of cells apparently have souls.

Now, we are long familiar with religious types using unintelligible concepts to salvage their inadequate arguments. But, in a spirit of intellectual ecumenicalism, let's do battle on their own territory.

It is well known that embryos are capable of splitting into identical clones (as happens in utero with twins). But, as ethicist John Harris has observed, what if a scientist divided an in-vitro embryo into four clones, each of which is viable and capable of being implanted? Presumably Christians would say that there are now four ensouled embryos. But what if they were then recombined? Would theists now say that three lives have been destroyed? Without the creation or destruction of a single cell?

The incoherence of the Christian position has not been fully confronted by the Government, despite the fact that the HFE Bill has been applauded for its liberalism. The continuing restrictions on embryonic experimentation demonstrate that ministers are content to compromise research in the “interests” of embryos, or, at least, as a sop to the religious lobby.

Another defect in the Bill has been brought into sharp relief by this weekend's announcement that scientists have created the first genetically modified embryo. A team from New York produced the embryo, which was destroyed after five days, to study how cells and diseases develop. While British scientists may soon be granted similar licences to modify embryos, it will remain illegal to implant them, even though the technology has the potential to correct diseases such as cystic fibrosis and even cancer.

But why do we resist these advances? Is it not time to recognise that the human genome is the product of an arbitrary process of evolution and that any safe method of modification that reduces human suffering or enhances potential should be grasped with both hands?

If the HFE Bill tells us anything, it is that we remain in hock to the moral conservatism of our Christian brethren.

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