Scottish scientists have found a way to harvest embryonic stem cells from eggs which have been discarded after IVF because they were unviable.

The discovery will increase the supply of vital stem cells available for research into illnesses such as Alzheimer's, Parkinson's and diabetes. It could also overcome some of the major ethical objections to stem cell research.

The breakthrough was announced yesterday by Roslin Cells Ltd, a spin-off company established in 2006 by the Roslin Institute.

The Edinburgh scientists took eggs which had failed to fertilise properly during IVF, and thus had no chance of developing into a viable embryo. The team developed techniques to stimulate them, so they divide and develop.

They then harvested embryonic stem cells, which can be used for research into liver disease, motor neuron disease and other conditions. Their work may lead to improvements in IVF technology, which will benefit infertile couples.

The discovery was announced in Australia, at the annual meeting of the International Society for Stem Cell Research. Dr Paul De Sousa, Roslin Cells' chief scientific officer, said: "Typically up to 30% of eggs in an IVF treatment cycle will be unusable as they fail to fertilise or do so abnormally.

"These eggs could not develop into a viable embryo and are normally discarded in routine IVF treatment.

"Until now, it was thought they are also incapable of producing embryonic stem cells. But what we have done here is found ways to recover' embryos from these eggs which have failed to fertilise."

There is currently a scarcity of embryos available for stem cell research. The majority of donated eggs are used for IVF, leaving very few for research purposes. Even then, their use is controversial.

Many argue that fertilised eggs should either be used to help couples conceive, or for research into ways of improving the success rate of IVF.

The new technique could get round this dilemma, and thus accelerate progress in developing new therapies for incurable genetic diseases.

The discovery was welcomed by the Genetic Interest Group, an alliance of patient organisations.

Alastair Kent, of GIG, said: "Embryonic stem cell research is a developing field that holds a great deal of promise for many of our members.

"Roslin's new process will deliver the dual benefits of reducing wastage of human eggs, and delivering more stem cell lines for research.

"We would hope that there are fewer ethical issues with this new technology, as the embryonic stem cells are derived from a human egg that had no chance of developing into a true embryo."

However, Josephine Quintavalle, director of comment on reproductive ethics, warned that the new technique raised many ethical questions.

She said: "If true, this would be an exciting, if extraordinary, development. But we remain sceptical.

"If they have indeed derived stem cells from abnormal eggs or eggs which have fertilised in an abnormal way, it is hard to imagine that any resulting stem cells would be free from abnormality.

"Also, it is hard to imagine how embryonic stem cells have been derived without at some stage creating an embryo."

Dr De Sousa said the team was not trying to "get around" such objections.

He said: "It is true that these recovered' embryos could potentially give rise to a viable conceptus. But it is equally possible that the conceptus would be abnormal, so we do not want to go down that route."

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