The Human Fertilisation and Embryology Authority is considering whether to recommend legalisation of "mitochondrial replacement" techniques designed to avoid the transmission of mitochondrial diseases (Report, 17 September 2012). We believe the benefits to a small number of parents are heavily outweighed by the risks to the child and to society. This would be the first instance of regulatory approval for modification of the human germ line. There is a long-standing international consensus that we should not cross this ethical line, since it is likely to lead to a future of genetically modified "designer" babies.

Such a slide has already been seen with drugs and surgery. The ugly beginnings of a eugenic market are already visible in the US, where Ivy League student donor eggs are priced 10 times higher than those of working-class women. Genetic enhancement also risks dehumanising and commodifying relationships between children and their parents. These downstream consequences cannot be ignored in making the present decision.

Mitochondrial replacement techniques also create significant epigenetic risks to the prospective child. Prevention of mitochondrial disease can be more safely and reliably accomplished through egg donation. The benefit of mitochondrial replacement is that it fulfils the mother's desire to be genetically related to her child. Such desires are understandable, but this is not a medical benefit. In our view, the benefit for a relatively small number of women of being genetically related to their child does not nearly justify the potential health risks to the child and the deleterious consequences of inheritable human genetic engineering.

Dr David King Human Genetics Alert, UK
Dr Marcy Darnovsky Center for Genetics and Society, USA
Professor Stuart Newman New York Medical College, USA
Dr Murdo Macdonald Science, Religion and Technology Project, Church of Scotland, UK
Dr Abby Lippman Professor Emerita McGill University, Canada
Professor Shree Mulay Memorial University, Canada
Dr Gina Maranto University of Miami, USA
Jaydee Hanson International Center for Technology Assessment, USA
Dr Tina Stevens Alliance for Humane Biotechnology, USA
Diane Beeson Professor Emerita California State University, USA
Dr Carmel Shalev Haifa University, Israel
Professor Charis Thompson University of California Berkeley, USA
Uta Wagenmann Gen-ethisches Netzwerk, Germany
Judy Norsigian Our Bodies Ourselves, USA
Hedva Eyal Isha L'isha, Israel