By DAVID DERBYSHIRE

Last updated at 09:19 02 April 2008

To make human stem cells, the Newcastle team say they must use the same technique that developed Dolly the sheep

Scientists have created the first part-human, part-animal embryo.

A team at Newcastle upon Tyne University inserted human skin cells into the hollowed-out egg cells of a cow - and jolted the egg into life.

The resulting embryo, which will eventually be used to investigate and treat diseases, survived for three days.

The scientists were only given permission to carry out the controversial experiment in January and the speed of their success has astonished scientists.

It comes a month before MPs vote on a Bill to explicitly make hybrid experiments legal. Currently, the law is ambiguous.

The Bill is highly controversial and last week Gordon Brown gave in to demands for a free vote on the issue.

The experiments have angered the Catholic Church and other religious leaders, who argue that the research is unnecessary and unethical.

But the Newcastle researchers say it could revolutionise medicine and provide cures for diseases such as Alzheimer's, Parkinson's, cystic fibrosis and Huntington's.

The team, led by Dr Lyle Armstrong, is trying to find a fast, cheap and reliable way of creating human stem cells.

These are the "parents" of every type of tissue in the human body and, in the right chemical conditions, can be turned into an almost limitless supply brain cells, muscle, skin or bone

To make stem cells, the researchers say they must first create human embryos using the same cloning technique developed for Dolly the sheep.

A single cell is taken from a human donor and its nucleus - containing a complete set of human genes - is removed.

This human DNA is then inserted into an donor egg cell whose own DNA has been sucked out. The egg is then sparked with electricity and starts to divide and grow.

The resulting embryo is a clone - genetically identical to the donor.

The Newcastle team say they would prefer to use human eggs for the experiments, but they are in too short a supply. Instead they are using cows' egg cells.

That means the embryos contain some cow DNA, although they look and behave like normal human embryos.

By law, the embryos have to be destroyed within 14 days of creation - when they are still smaller than a pinhead.

Professor John Burn from Newcastle University said: "This is licensed work which has been carefully evaluated.

"This is a process in a dish, and we are dealing with a clump of cells which would never go on to develop.

"It's a laboratory process and these embryos would never be implanted into anyone."

Critics say the Bill legalising creation of hybrids is immoral.

"It is difficult to imagine a single piece of legislation which more comprehensively attacks the sanctity and dignity of human life," Cardinal Keith O'Brien, archbishop of St Andrews and Edinburgh said last week.