The UK Parliament's rejection of an amendment to new fertility legislation could delay the only potential new treatment for a class of roughly 50 devastating inherited metabolic disorders from becoming available for possibly years beyond when the technology is proven safe and effective for clinical use, according to scientists. Dawn Primarolo, the health minister, announced last week that before the Human Fertilisation and Embryology Authority (HFEA) becomes able to license clinics to perform this procedure, further public consultation is required.

The technology is controversial because it involves sperm from one man and two eggs from different women, dubbed by the media as 'three-parent' embryos. The media and pro-life campaigners have flagged concerns that regulation allowing the manipulation of an embryo's genetic makeup is a step towards genetically engineering designer babies. Others believe that the use of two woman's eggs confuses and degrades the family unit. However, supporters have accused the media of sensationalising the issue. Professor John Burn at Newcastle University denies the method would lead to designer babies and describes it as similar to replacing a radio battery. 'You are not altering the radio at all, just giving it a new power source', he said.

Experts estimate that the technology could be available to women in as little as three years but fear that by not specifically incorporating the technique into the legislation, the Government will delay the treatment from becoming available by forcing scientists to seek permission from the Health Secretary and possibly even parliament, which are likely to become ensnared in ethical debate and public consultation thereby depriving the 150 babies born each year in the UK with mitochondrial-related diseases of possible life-saving treatment. Mark Simmonds, the Conservative MP who proposed the amendment felt that 'such a significant scientific breakthrough should have been included in the Bill.'

There are currently no available cures but scientists at Newcastle controversially received a license, after an initial refusal from the HFEA, in 2005, to research a breakthrough technique that involves the removal of a newly-fertilised egg's nuclear DNA, and transplanting it into an egg from another woman which is also denucleated. The resulting embryo would have mitochondria from one woman, but its remaining estimated 25,000 nuclear  genes would derive from the mother and father who provided the fertilised egg. This technique would replace the defective mitochondrial DNA with healthy mitochondrial DNA from the host egg. The resulting child would have all of the visible genetic traits of the intended parents and would bear less than 0.1 per cent genetic similarity to the mitochondrial donor expressed through metabolic function alone.

The technology eradicates the mitochondrial disorders which are linked to mutations in a tiny subset of approximately 37 genes located outside the cell nucleus - which contains the remainder of the estimated 25,000 overall genes - within the 1,000 to 10,000 mitochondria housed in each of our cells. Mitochondria function as the cell's 'power-source'. Mitochondrial genes are not expressed as physical traits but rather encode for the vital chemical processes responsible for the metabolic release of cellular energy. These disorders follow a maternal inheritance pattern and harmful genetic mutations in these few but essential genes can have a catastrophic effect causing a range of disorders that affect one person in every 6,500, causing liver failure, blindness, and forms of epilepsy and muscular dystrophy.