Women who are infertile because they have no eggs of their own could mother children using any cell in their bodies, suggest scientists.

A revolutionary technique inserts the genes from the mother into a donor egg, which is then fertilised by the father's sperm.

Currently, the only hope of becoming a mother is to use a donated egg, and bear a child which carries the donor woman's genes and not her own.

However, experts have urged caution in the development of the procedure - one described it as "just one step away from cloning".

The breakthrough was made by a team at Cornell University in New York, US, who experimented on human eggs donated during IVF.

First, they removed the nucleus containing the donor's genetic material from the egg, then injected a normal cell from ovarian tissue.

A normal mature egg contains only "half a set" of chromosomes - it is awaiting the arrival of the sperm, which contains the other half so that an embryo can be created.

Electric shock

Earlier in its development, the immature egg is like any other normal cell, and has a full set of genetic instructions, and has to jettison half to become prepared for possible fertilisation.

The "somatic" cell injected by the Cornell researchers also has a full set - so half have to be removed before fertilisation can occur.

To do this, the researchers harnessed the natural ability of the egg to make this happen, using a tiny electrical current, or chemicals, to activate the process of splitting the normal cell's nucleus in half.

One half is then taken out, and the genetic material from the sperm inserted.

Despite trying the procedure on more than 150 eggs, in only a handful of cases did any cell division, which might suggest fertilisation, occur.

Any cell used

Dr Takumi Takeuichi, who presented the research at the European Society for Human Reproduction and Embryology meeting in Lausanne, said that he felt it might be possible to use just about any cell in the woman's body.

He said: "Many women can't produce their own eggs - for example, if they are past the menopause - and many still want to have genetically related offspring.

"This treatment might be able to help them contribute their own genome."

He said that fuller animal trials were essential before the technique could be transferred into the fertility clinic for humans.

However, the technique is so close to the "cloning" technology used to create Dolly the sheep that it will raise difficult ethical questions for doctors.

In addition, the finished baby will effectively contain DNA from three people - its mother, father, and a tiny amount of mitochondrial DNA from the donor which is retained.

Professor Lyn Fraser, the chairman of ESHRE, told BBC News Online that doctors should proceed with caution.

She said: "There are so many unknowns. There are some techniques that you might say: 'I can do this, but should I be doing this?'"