Scientists have inched closer to producing a controversial "three parent baby" after they successfully fertilised an egg with two biological mothers, a development likely to provoke an ethical storm over hybrid or genetically modified children.

The research led by Atsushi Tanaka of St Mother Hospital in Kitakyushu, Japan, has shown that eggs donated by young females could be used to repair the damaged eggs of older women, increasing the chances of successful fertilisation.

Though they are yet to use the eggs to produce babies, they injected them with sperm to produce an early stage embryo in the laboratory.

Tanaka team removed the nuclei from 31 eggs collected from women undergoing IVF and injected them into enucleated eggs donated by women aged under 35. Of these, 25 eggs looked viable.

When injected with sperm, 7 eggs or 28 per cent formed early-stage embryos called blastocyts, compared with just 3 per cent of the unrepaired eggs, the 'New Scientist' reported on Thursday.

The research is likely to provoke an ethical outrage as critics believe it could lead to hybrid or genetically modified children.

"If we could transfer these constructed new embryos, I believe the success rate would be high," Tanaka, the lead researcher was quoted as saying by the 'New Scientist'.

Tanaka presented his results at the American Society for Reproductive Medicine meeting in Atlanta, Georgia last month. With colleagues in the US and Spain, he now plans to transfer embryos from repaired eggs into women.

IVF often fails in older women and one reason is thought to be abnormalities in the cytoplasm of their eggs.

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