The Nuffield Council on Bioethics has published an ethical review of new techniques which aim to prevent the transmission of faulty mtDNA from mother to child. The report concludes that such techniques are ethically permissible, provided that further research establishes their safety.

The Council said the benefits of children being born free of mitochondrial disorders outweigh the ethical concerns raised over the potential use of the techniques. It also highlighted the benefits of women carrying mutated mtDNA being able to have children who are genetically related to them, and ensuring that subsequent generations are also free from mitochondrial disorders.

Dr Geoff Watts, chair of the Council's working group, 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'.

Errors in mtDNA which are inherited down the maternal line can lead to serious health disorders (reported in BioNews 641) in both men and women. There are currently no cures for such disorders.

The new techniques, which are not currently permitted for use in treatment under UK law, aim to prevent only the transmission of mitochondrial disorders caused by mutated mtDNA (as distinct from mitochondrial disorders caused by nuclear DNA). There are two techniques - pronuclear transfer and maternal spindle transfer - which both involve using healthy mitochondria from a donated egg, thereby creating children with a genetic connection to three people.

The Council examined ethical concerns that the techniques may constitute germline therapy. It also considered whether children born with genetic contributions from three people may have confused perceptions of their identity, and whether the use of the techniques could create the potential for harm to future generations. The report concludes that the proposed treatments do indeed constitute germline genetic modification, albeit a circumscribed form of modification where DNA molecules are left completely intact, thereby avoiding risks posed by intervening in the gene sequence within the DNA molecule.

'We understand that some people concerned about the idea of germline therapies may fear that if such treatments for mitochondrial gene disorders were approved, a ''slippery slope'' would be created towards comparable alterations to the nuclear genome', said Dr Watts. 'However, we are only talking about the use of these techniques in the clearly-defined situation of otherwise incurable mitochondrial disorders, under strict regulation', he added.

The report also rejects the notion of the mitochondrial donor representing a 'third parent', either in legal or in ethical terms, and finds no evidence that mitochondrial inheritance is an element of personal identity. The report concludes that mitochondrial donors should not have the same status in law as reproductive egg donors.

Clinical geneticist and member of the working group, Professor Frances Flinter, said: 'As far as we know, mitochondrial genes alone create no unique identifiable genetic link between the child and donor. The child's recognisable likeness to family members would come from their parents' nuclear DNA. Given these, and other reasons, we think it is both legally and biologically inaccurate to refer to a mitochondrial donor as a ''second mother'' or ''third parent'' to the child'.