Babies could be conceived with three genetic parents in the UK by the end of next year.
This is after the Department of Health opened the door to controversial treatments for inherited diseases.
The landmark decision intends to make use of donated DNA from a second donor "mother", in a bid to stamp out serious mitochondrial diseases that can be passed from a mother to her children.
Procedures will be issued for public consultation later this year and then debated in Parliament. If MPs find them ethically acceptable, the UK could become the first country in the world to permit the In-Vitro Fertilisation (IVF) treatments.
It is envisaged that between five and 10 "three parent" babies would be born each year, altering the "germ line" made up of inherited DNA for the very first time.
Only the tiny amount of DNA in a cell's "battery packs", the mitochondria, would be changed by the procedures. DNA in the nucleus, which determines individual characteristics such as facial features and eye colour, would remain untouched.
But while some people see the move as a way of treating inherited diseases, others believe it would mark a slippery slope leading to "designer babies" and eugenics.
Around one in 200 babies are born each year in the UK with defects in the mitochondria, rod-like bodies that supply cells with energy.
Meanwhile, one in 6,500 is seriously affected and can suffer potentially life-threatening diseases including a form of muscular dystrophy and conditions leading to hearing and vision loss, heart, lung and liver problems, and bowel disorders.
Copyright Press Association 2013