MARK STEAD charts the Parliamentary battle which lay behind the victory for those backing the creation of human-animal hybrids, as favoured by Prime Minister Gordon Brown.

TO its supporters, it's groundbreaking research which could ensure huge strides are made in the search for a cure to diseases such as Alzheimer's and Parkinson's.

To its opponents, it's the grotesque manipulation of nature which will allow scientists to trample over decency.

Whatever your stance, the creation of human-animal hybrids to allow embryonic stem cells to be produced for research will now be allowed - but it was not a battle the Government was able to win without a fight.

Following days of intense, impassioned and emotional lobbying from both sides of the debate, 336 MPs voted against a cross-party attempt to impose a blanket ban on hybrids, with 176 MPs defying the Government.

Prime Minister Gordon Brown has hailed stem cell research as an "inherently moral endeavour" and a "profound opportunity" to save and transform lives.

He has said he has "deep respect" for people who disagree with the Bill, but reasons that "we owe it to ourselves and future generations" to support such research.

And he speaks with a personal tongue as well as a political one - his son, Fraser, has cystic fibrosis, a condition which could benefit from embryo research Meanwhile, a bid to ban "saviour siblings" - babies selected to provide genetic material for seriously ill relatives - was also defeated as debate about the updating of the Human Fertilisation And Embryology Bill to bring it into line with modern scientific advances raged in the House of Commons.

MPs were last night voting on an amendment to the Bill which is asking for the upper time limit on abortions to be reduced from 24 weeks to 20 weeks or less.

However, it is the decision on embryo research which has focused most people's minds over the past few days - among them Selby MP John Grogan.

A practising Catholic, he was one of the 176 MPs to rebel against the party he supports in the free vote on human-animal hybrids, and he admits it tore at his conscience.

"I voted the way I did because I was not convinced for two reasons," he says.

"My first concern was whether there would be substantial benefits from this research which could not be achieved through other forms of stem cell research. Secondly, I felt Parliament has to draw lines between what is considered acceptable and not acceptable.

"I'm uneasy about mixing human-animal embryos. I've listened to what people say, such as other ministers, the Catholic Church and my constituents, and in the end I have to make my mind up on the basis of an informed conscience.

"I'm a proud Catholic and a proud member of the Labour party. Sometimes in politics, there are conflicts in your different personal beliefs, but you have to resolve them on the basic of your conscience."

Mr Grogan admits he is "disappointed" at the outcome of the embryo vote, saying: "I think it was a good debate and perhaps an advertisement for the virtues of having free votes from time to time.

"But while I'm not predicting Armageddon, I just think a line has been crossed after which the consequences cannot be foreseen. It may be that, through other forms of stem cell research, there comes a time where we no longer have any justification for animal-human hybrids."

Father Pat Hartnett, the parish priest at St George's RC Church, in Peel Street, York, echoes the Catholic Church's concern - that a fertilised embryo should be regarded as human and should not be destroyed or terminated.

"All life is sacred and all life is a gift," he said.

"We need to use science and understanding under proper guided ways. There is such a thing as something being right and something being wrong, and there are other ways in which information can be found out without having to go down this particular road.

"We are the only European country which is allowing this and I do find it regrettable. I certainly have fears about what it might lead to - it seems not enough information is there and there is a lot of unease about it in people's minds."

But the Bill has its defenders, among them Simon Denegri, the chief executive of the Association of Medical Research Charities.

"MPs have clearly listened to the strong arguments put forward by medical research charities, patients groups and scientists of the importance of this research to advancing our understanding of diseases which affect hundreds of thousands of people and their families in the UK," he said.

"At a time when we still have so much to learn about the causes of such conditions, it is important that we pursue the many scientific avenues open to us within a robust regulatory framework.

"The Bill achieves this. It is a good piece of legislation and its successful passage is in the public interest."


WHAT HAVE MPS VOTED FOR?

The extension of stem cell research using embryos by permitting human-animal hybrids, known as cytoplasmic or admixed' embryos, to be created.

WHAT IS A HYBRID EMBRYO?

A mixture of human and animal tissue. Some British scientists want to carry out experiments which would involve transferring nuclei containing DNA from human cells - such as skin cells - into animal eggs which have had almost all of their genetic information removed.

The resulting embryos would be more than 99 per cent human with a small animal component and would be kept for up to 14 days to allow stem cells to be harvested.

WHY USE ANIMAL EGGS?

Creating hybrid human-animal hybrids was originally suggested as a way of dealing with the fact there is a shortage of human eggs available for research, due to the painful and potentially dangerous process of donation.

Experts have also said using human-animal mixes rather human eggs to create stem cells is less cumbersome and produces better results.

WHAT WOULD IT ACHIEVE?

According to scientists, embryonic stem cells will allow them to study different disease processes - for example, they could take genetic material from a person with Parkinson's Disease and put it into an empty animal egg to make stem cells carrying the same genetic defects which cause the disease. It is also possible that, in the future, cells cloned from individual patients could be transplanted to cure diseases.

WHAT ARE THE FLASHPOINTS?

The move has been variously condemned as illegal, immoral, unethical, "Frankenstein research" and "tampering with nature" by its critics, who say embryo research in general has led to few scientific advances.

There have also been claims - strongly refuted by scientists - that it will pave the way for animal-human hybrids to be created.