Pioneering IVF treatment developed in Newcastle is one step closer after ministers agreed to amend fertility laws.
The draft regulations could see babies born from three genetic parents.
The aim is to eliminate inherited diseases by replacing faulty DNA in egg cells with donated DNA from another egg.
The government has launched a three-month consultation, but critics argue it could lead to designer babies.
Paul Tully from the Society for the Protection of Unborn Children said the "three parent" IVF technique is a "step" towards designer babies.
Mr Tully told ITV News: "It is a change that can be passed on to future generations, and we are manipulating the genes of a child.
"We're concerned that we are replacing what we know to be defective DNA in the embryos that we don't like with what we think is good DNA - but we can't be sure.
"Putting the money into this kind of research is denying funding to research which is needed and ongoing to help people with mitochondrial diseases and other diseases in other ways.
"We've seen the same thing before with stem cell research, we've seen it with IVF - promises that using embryos will lead to advances but come to nothing.
Dr David King, director of Human Genetics Alert, told ITV News the "three parent" IVF technique crosses a "crucial ethical line":
Genetic Alliance UK has welcomed the "three parent" IVF technique proposal.
The charity's director, Alastair Kent, said: "Many of these [mitochondrial] conditions are so severe that they are lethal in infancy, creating a lasting impact upon the child's family.
"An added option for families at risk of having a child with such a condition is welcome".
Experts said the technique would likely be used in around a dozen IVF cases every year.
The director of the Human Genetics Alert campaign group said the IVF technique used to create babies with three genetic parents is "unnecessary" and "ethically unsound".
Dr David King also criticised the Government for failing to conduct a more comprehensive public consultation on the issue.
Dr King told Reuters, "They cross the ethical line that has been agreed by Governments around the world that we should not genetically alter human beings".
Some groups say the proposals for three parent babies are causing worldwide concern:
The Chief Medical Officer for England, Professor Dame Sally Davies, explains that the 'three parent' technique does not tamper with the nucleus. It simply moves it into a cell which has healthy 'battery packs', known as mitochondria, which power the nucleus properly and eradicate serious disease.