A controversial fertility treatment which creates embryos from two women and one man to prevent life-threatening disorders is ethical, a report says.

Children born through "three-person IVF" would contain some genetic material from three people.

The UK's Nuffield Council on Bioethics said the technique could free children from "very severe and debilitating disorders".

Other groups said the procedure was unnecessary and dangerous.

The aim of the technique is to replace faulty mitochondria, the body's tiny power stations. There are hundreds and sometimes thousands of them in every cell in the body.

They come with their own genetic material, known as mitochondrial DNA, which sometimes can become mutated and defective.

As a result, one in 6,500 children in the UK are born with "mitochondrial disorder" which causes muscle weakness, blindness and heart failure.

'Social benefits'

Mitochondria are passed down only from mother to child. "Three-person IVF" takes the core genetic information from mother and father as usual, but puts it into a donor egg which contains healthy mitochondria.

It means the child would have 0.1% of its genetic information coming from the donor.

Prof Peter Braude, from King's College London, said: "The net effect is an embryo that carries the true parents characteristics in a clean egg with healthy mitochondria."

Image caption Hundreds of mitochondria in every cell provide energy

For the past eight months the respected Nuffield Council on Bioethics has been assessing the issue .

Dr Geoff Watts, who led the inquiry, said: "If further research shows these techniques to be sufficiently safe and effective, we think it would be ethical for families to use them if they wished to, provided they receive an appropriate level of information and support.

"They could offer significant health and social benefits to individuals and families, who could potentially live their lives free from what can be very severe and debilitating disorders."

It also said the donor woman would not be a "third parent" or "second mother" and the laws on sperm or egg donation should not apply.

'Slippery slope'

One area of concern surrounding the technique is that the effects would be passed on from generation to generation.

Dr David King, the director of Human Genetics Alert, said: "Just as Frankenstein's creation was produced by sticking together bits from many different bodies, it seems that there is no grotesquerie, no violation of the norms of nature or human culture at which scientists and their bioethical helpers will balk.

"The proposed techniques are both unnecessary, and highly dangerous in the medium term, since they set a precedent for allowing the creation of genetically modified designer babies."

He argued that such techniques would affect many generations and crossed "what is normally considered the most important ethical line in the prevention of a new eugenics" and this was "precisely how slippery slopes get created".

The Human Fertilisation and Embryology Authority will start a public consultation in September and will report its findings next year.

The Wellcome Trust recently funded Newcastle University to continue to research the technique.

Its director, Sir Mark Walport, said: "I am delighted to see that its report has found use of the techniques ethical.

"We urge the government to outline a timetable for considering amendments to legislation to permit use of the techniques in the clinic if, as we hope, the Human Fertility and Embryology Authority's consultation in autumn shows public support for this important technology."