File photo: A team at Oregon Health and Science University in the US successfully modified scores of human embryos. Picture: AP

London - The creation of "designer babies" has taken a step forward, it was reported.

Scientists have successfully modified a human embryo in contrast to previous attempts which have failed to reliably take out defective genes.

The revolutionary gene editing technique Crispr cuts out defective sequences and replaces them with ‘safe’ sequences. It has been compared to "cut and paste" in a word processing software.

A team at Oregon Health and Science University in the US successfully modified scores of human embryos.

They were checked after two or three days to ensure a faulty gene had been eliminated but not allowed to grow, reported the Massachusetts Institute of Technology Review.