The United Kingdom became the first country on Thursday to formally license an in-vitro fertilization treatment designed to create babies from three people.

Critics of the treatment say it is a dangerous step that will lead to the creation of genetically modified "designer babies".

In a long-awaited decision, the country's Human Fertilization and Embryology Authority gave the final go-ahead for the treatment known as mitochondrial transfer, which doctors say could help prevent incurable inherited diseases.