Experiments to create Britain’s first embryos that combine human and animal material will begin within months after a government watchdog gave its approval yesterday to two research teams to carry out the controversial work.

Scientists at King’s College London, and the University of Newcastle will inject human DNA into empty eggs from cows to create embryos known as cytoplasmic hybrids, which are 99.9 per cent human in genetic terms.

The experiments are intended to provide insights into diseases such as Parkinson’s and spinal muscular atrophy by producing stem cells containing genetic defects that contribute to these conditions. These will be used as cell models for

investigating new approaches to treatment, and to improve the understanding of how embryonic stem cells develop. They will not be used in therapy, and it is illegal to implant them into the womb. The decision, taken by the by the Human Fertilisation and Embryology Authority (HFEA), to grant one-year licences to both teams ends more than a year of uncertainty for the researchers, who first applied for permission in the autumn of 2006.

Last January the authority deferred its decision and began a consultation on the issue, which reported in September that the public was broadly supportive. In late November, it again delayed ruling because of concerns about procedures for obtaining consent from the donors of the human DNA to be used.

While the HFEA was deliberating, the Government proposed a ban on the creation of human-animal embryos, also known as “cybrids”, but retreated after a revolt by scientists.

The creation of human-animal embryos will be explicitly permitted by the Human Fertilisation and Embryology Bill currently passing through Parliament, subject to HFEA licensing. An amendment that would have blocked such research was defeated in the House of Lords on Monday by a majority of 172. Stephen Minger, who leads the King’s team, said yesterday he was delighted that he would be able to start the experiments. “I am pleased that the HFEA has finally after a year and a half realised the importance that the work that we and the group from Newcastle have been licensed for,” he said.

Lyle Armstrong, who leads the Newcastle group, said: “Finding better ways to make human embryonic stem cells is the long-term objective of our work and understanding reprogramming is central to this. Cow eggs seem to be every bit as good at doing this job as human eggs so it makes sense to use them since they are much more readily available, but it is important to stress that we will only use them as a scientific tool and we need not worry about cells derived from them ever being used to treat human diseases.”

Some critics of cybrid embryos have argued that their use is no longer necessary, given the recent development of a reprogramming technique that can turn back the clock on adult tissue to make “induced pluripotent” stem cells with embryo-like properties, but the HFEA licence committee rejected this.

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