LONDON, Feb 1 (Reuters) - Scientists in Britain have been give the go-ahead to edit the genes of human embryos for research purposes, using a technique that some say could eventually be used to create "designer babies".

Less than a year after Chinese scientists caused an international furor by saying they had genetically modified human embryos, Kathy Niakan, a stem cell scientist from London's Francis Crick Institute, was granted a license 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".

The scientists will not be allowed to develop the modified embryos for clinical purposes or implant them into any women.

Niakan plans to carry out her experiments using what is known as 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. Many experts have called it "game-changing".

David King, director of the UK campaign group Human Genetics Alert, said Niakan's plans would eventually lead to "a future of consumer eugenics".

"This research will allow the scientists to refine the techniques for creating GM babies," he said in a statement.

But Sarah Norcross, director of Progress Educational Trust, which campaigns for ethically sound research in genetics, said the HFEA's decision was "a victory for level-headed regulation over moral panic".

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 such as in vitro fertilization (IVF).

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The work will be carried out on embryos that have become surplus to donor patients IVF treatment.

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.

(Reporting by Kate Kelland; Editing by Editing by Jeremy Gaunt)