Researchers from Newcastle University are to be allowed to fuse the contents of two human eggs to create an egg in effect derived from two women that could be fertilised with the sperm of a man. The aim eventually is to use the technique to overcome a form of inherited disease resulting from genetic damage to the tiny "power houses" or mitochondria of the cell, which are inherited from the mother.

Although the technique is similar to the cloning method of transferring a cell nucleus into an egg, it will not result in a cloned baby as sperm will still be used for in-vitro fertilisation.

Scientists intend to use two eggs because they want to produce an egg with healthy mitochondria by taking the cell cytoplasm from a donor woman and combining it with the nucleus of an egg taken from a woman with mitochondrial disease who wants to have her own genetic child.

A committee of experts has ruled that the experiment can go ahead after the Human Fertilisation and Embryology Authority (HFEA) initially rejected a licence application by a team led by Professor Doug Turnbull of Newcastle's Centre for Life. The HFEA had argued that the wording of the Fertility Act prevented it from giving a licence because it prohibits "altering the genetic structure of any cell while it forms part of an embryo".

Professor Turnbull lodged an appeal earlier this year and the HFEA's appeals committee yesterday ruled that the licence should be given to the Newcastle scientists because of the importance of the research in terms of finding a way of allowing mothers with mitochondrial disease to have healthy children.

"The appeal committee heard a range of evidence on the genetics behind the research proposed and how the HFE Act should be interpreted. Expert views were given on the meaning of 'genetic structure' and the committee heard that this phrase has no precise scientific meaning," an authority spokesman said.

"After having satisfied itself that the research would be permissible under the HFE Act, the appeal committee went on to consider the detail of the application. Having satisfied itself that the research activities were 'necessary and desirable' under the criteria in the HFE Act and that the use of embryos was necessary for the research, the committee ruled that a licence for this research should be granted," he said.

The appeals committee included leading authorities on genetics and embryology such as Professor Martin Bobrow of Cambridge University, Anne McLaren, who was a member of the Warnock Committee in the 1980s, and Professor John Burn of Newcastle University.

Mitochondrial disorders cause major health problems in children, many of whom die prematurely as they are unable to produce the energy for growth.

The mitochondria exist outside the nucleus, in a cell cytoplasm and have their own genetic material in the form of DNA ­ the only DNA outside the cell nucleus. All the mitochondria are passed on from a mother's egg with none being contributed by the sperm cell. At present there is no effective treatment for mitochondrial disease.

Women can have a very mild form of the condition or even be unaware of having it yet their children can be severely affected. There is no way at present to prevent an affected woman from having a child at risk.

However research on mice suggests it may be possible to overcome this by using the eggs of healthy donors. The technique involves taking the pro-nucleus of an egg ­ which develops from the nucleus ­ and injecting it into an egg with healthy mitochondria and no nucleus of its own.