Scientists in Britain have been given the go-ahead to edit the genes of human embryos for research, using a technique that some say could eventually be used to create "designer babies."

Less than a year after Chinese scientists caused an international furore by saying they had genetically modified human embryos, Kathy Niakan, a stem cell scientist from London's Francis Crick Institute, was granted a licence to carry out similar experiments.

"The Human Fertilisation and Embryology Authority (HFEA) has approved a research application from the Francis Crick Institute to use new 'gene editing' techniques on human embryos," Niakan's lab said on Monday.

It said the work carried out "will be for research purposes and will look at the first seven days of a fertilized egg's development, from a single cell to around 250 cells."

Ethical concerns

Niakan plans to carry out her experiments using CRISPR-Cas9, a technology that is already the subject of fierce international debate because of fears that it could be used to create babies to order.

CRISPR can enable scientists to find and modify or replace genetic defects, and many of them have described it as "game-changing."

Around the world, laws and guidelines vary widely about what kind of research is allowed on embryos, which will change the genes of future generations. In the U.S., the National Institutes of Health won't fund this kind of research but private funding is allowed.

In Canada, it's been used in all sorts of research. The Hospital for Sick Children in Toronto used it to correct the mutation that causes Duchenne muscular dystrophy.

But critics warn that tweaking the genetic code this way could eventually produce a slippery slope that leads to so-called "designer babies," where parents seek taller, stronger or smarter children with specific physical characteristics.

David King, director of the U.K. campaign group Human Genetics Alert, has called Niakan's plans "the first step on a path ... towards the legalization of [genetically modified] babies."

Could improve infertility treatments

Niakan says she has no intention of genetically altering embryos for use in human reproduction, but wants to deepen scientific understanding of how a healthy human embryo develops, something that could, in the long term, help to improve infertility treatments.

At a briefing for reporters in London last month, she said the first gene she planned to target was one called Oct4, which she believes may have a crucial role in the earliest stages of human fetal development.

Bruce Whitelaw, a professor of animal biotechnology at Edinburgh University's Roslin Institute on Scotland, said the HFEA's decision had been reached "after robust assessment."

"This project, by increasing our understanding of how the early human embryo develops and grows, will add to the basic scientific knowledge needed for devising strategies to assist infertile couples and reduce the anguish of miscarriage," he said in an emailed comment.

At an international meeting in Washington last year, scientists agreed that efforts to research the possibility of gene editing should continue, despite the ethical and legal problems the technique raises.

Last year, British lawmakers voted to allow scientists to create babies from the DNA of three people to prevent children from inheriting potentially fatal diseases from their mothers. In doing so, it became the first country in the world to allow genetically modified embryos to be transferred into women.