Fertility chiefs have been accused of putting science before ethical principles after giving the go-ahead for scientists to edit the genes of human embryos.
The decision by the Human Fertility and Embryology Authority (HFEA), which regulates fertility scientists, means the UK the first country in the western world to allow such research.
Scientists led by Dr Kathy Niakan, at the Francis Crick Institute in London, have been granted a licence to "cut and paste" the DNA of donated embryos as part of an investigation into miscarriage.
The work is controversial because it involves altering "germline" DNA that is inherited.
All the embryos used will must be destroyed after two weeks and it will be illegal to implant them into a womb.
But critics say the HFEA has ignored warnings, acted too hastily, and set scientists on the start of a slippery slope towards the creation of genetically modified "designer babies".
Dr David King, director of the watchdog group Human Genetics Alert, said: "This research will allow the scientists to refine the techniques for creating GM babies, and many of the Government's scientific advisers have already decided that they are in favour of allowing that.
"This is the first step in a well mapped-out process leading to GM babies, and a future of consumer eugenics."
Anne Scanlan, from the pro-life organisation Life, said: "The HFEA now has the reputation of being the first regulator in the world to approve this uncertain and dangerous technology. It has ignored the warnings of over a hundred scientists worldwide and given permission for a procedure which could have damaging far-reaching implications for human beings.
"We are .. concerned that such controversial intervention in the human germline opens up the very real possibility of eugenics where the existence of human beings becomes conditional on the possession of certain physical characteristics."
Josephine Quintavalle, from the group Comment on Reproductive Ethics (Core), accused the HFEA of "arrogance". She pointed out that a Nuffield Council expert panel looking at the ethics of gene editing had only completed its consultation yesterday.
"This is a very contentious and extremely dangerous area of embryo manipulation which is eliciting worldwide concern, and at the very least the HFEA should have waited until Nuffield had had a chance to examine responses," said Ms Quintavalle.
In sharp contrast, members of the scientific establishment lined up to congratulate the HFEA on its decision and welcomed the announcement.
Professor Peter Braude, an expert in obstetrics and gynaecology from King's College London, said: "I am delighted to hear that the HFEA have had the good sense to approve this important project.
"Gene editing tools will allow fresh insights into the basic genetic mechanisms that control cell allocation in the early embryo."
Darren Griffin, Professor of Genetics at the University of Kent, called the ruling "a triumph for common sense". Dr Rob Buckle, director of science programmes at the Medical Research Council, said: "Today's decision by the Human Fertilisation and Embryology Authority cements the UK's position as a global leader for research."
Dr Niakan's team wants to use a sophisticated new technology called CRISPR/Cas9 to make precise changes to the genetic code of human embryos by slicing up DNA using "molecular scissors".
All the embryos will be donated by couples undergoing IVF treatment who no longer need them.
Technically the application still has to be approved by the local Research Ethics Committee, made up of scientists, health professionals and lay-members, but this is no more than a rubber-stamping procedure.
A statement from the HFEA said: "Our Licence Committee has approved an application from Dr Kathy Niakan of the Francis Crick Institute to renew her laboratory's research licence to include gene editing of embryos.
"The committee has added a condition to the licence that no research using gene editing may take place until the research has received research ethics approval.
"As with all embryos used in research, it is illegal to transfer them to a woman for treatment."
Earlier this year, Dr Niakan said the aim was to improve understanding of the genes needed for a human embryo to develop into a healthy baby.
She added: "The reason why it is so important is because miscarriages and infertility are extremely common, but they're not very well understood."
In April last year, a Chinese team reported the world's first attempt to use CRISPR/Cas9 to modify the DNA of human embryos.
The 16 researchers from Sun Yat-Sen University in Guangzhou wanted to see if it was possible to correct the gene defect behind the blood disorder beta-thalassaemia.
They did not try to create a pregnancy and only used embryos that were abnormal, unlike the Francis Crick Institute scientists who will experiment on healthy embryos.
While in some cases the Chinese team was successful, in others the technology did not work or introduced unexpected mutations.