Scientists have called on the Government to give the immediate green light to allowing three-parent babies after experts ruled the techniques were safe.
The Human Fertilisation and Embryology Authority (HFEA) said it had examined a "voluminous" amount of data and concluded the techniques were not "unsafe" and "potentially useful".
But it added that further experiments, including on human embryos, were needed.
In the procedure, donor DNA is taken from a "second mother" implanted into a defective egg to prevent children suffering debilitating conditions such as muscular dystrophy.
The technique, which has been developed by British scientists, is currently banned, but supporters want a change in the law saying it would allow affected couples the chance to have their own, genetically-related healthy children.
It is controversial because it would result in babies having DNA from three people and critics have warned it could lead to the creation of "designer children".
The Government started a consultation on draft regulations in February - paving the way for the technique to be permitted and for the UK to become the first country to have three-parent babies.
As part of the consultation, the Department of Health asked a panel of experts from the HFEA to examine the safety and effectiveness of two techniques.
Maternal Spindle Transfer (MST) and Pronuclear Transfer (PNT) are both techniques in which damaged mitochondria from a mother-to-be are replaced with healthy ones from an egg donated by another woman.
Faults in mitochondria - small structures in cells which produce much of the energy needed by the cell - cause serious illness in one in 6,500 babies and are responsible for 50 genetic diseases, many of which kill in infancy.
Women carrying damaged mitochondria can also miscarry repeatedly.
Today, the HFEA panel announced the conclusions of its third review, following two similar reviews in 2011 and 2013.
Professor Robin Lovell-Badge said: "The panel's view still stands, that both techniques have the potential to be useful for all patients with disorders caused by mutated mitochondrial DNA.
"There has been a lot of new data that we looked and we worked very hard to address all the issues...
"First of all, there is still no evidence to suggest that either techniques might be unsafe. There is still insuffient evidence to recommend one technique over the other... but we still do recommend that some further experiments are needed to be done before introducing either into clinical practice."
Professor Peter Braude, also on the panel, said there was already a "waiting list" of women wanting to have the procedure.
It is not known how many women have expressed an interest in mitochondrial replacement transfer but in February, the Department of Health said that initially, just ten babies with three genetic parents were expected to be born annually, but this could climb to 125.
Dr Andy Greenfield, panel chair, said: "I want to emphasise that safety is paramount in our consideration but is not a straight forward issue."
He compared the concerns to those raised ahead of the introduction of IVF in the 1970s. "All these questions were asked then," he said.
Addressing critics he said: "I would like to stress a couple of things, these techniques are not related to, nor will lead to, reproductive cloning.
"Individuals created by mitochondrial replacement are unique individuals ... so this is sexual reproductoin with a twist.
"Secondly this is not eugenics...eugenics it seems to me invokes preventing some individuals being born... These technologies will allow women to have genetically related and healthy children.
"The mandate for this panel was the science, the research and the data, not ethics."
Afterwards, Dr Jeremy Farrar, director of the Wellcome Trust Britain's biggest research charity, urged government to pass laws as soon as possible.
He said: “We are extremely pleased that the latest scientific review of mitochondrial donation techniques has confirmed that there is no evidence to suggest either technique is unsafe, and that both could help families affected by serious mitochondrial disease.
"Given this evidence, we urge Parliament to pass enabling regulations swiftly, to ensure that there is no delay in patients being able to access these life-changing techniques.”
Alastair Kent, director of Genetic Alliance UK, said: "Here is another clear signal that we are nearing the level of evidence that will be sufficient to bring mitochondrial donation to families in the UK affected by mitochondrial DNA conditions.
"This increases the urgency to finalise the regulations to permit the use of this technology that were the subject of a recent consultation.
"We should be waiting for the science to be ready, not for the regulations, and the science is moving quickly."
A Department of Health spokesman said: “Mitochondrial donation will give women who carry severe mitochondrial disease the opportunity to have children without passing on devastating genetic disorders.
"It will also keep the UK at the forefront of scientific development in this area.
“We will give careful consideration to this report together with the responses to our recent consultation and announce our plans in the next few months.”
If rules are brought in, it will be up to the fertility regulator, the Human Fertilisation and Embryology Authority (HFEA), to decide whether a treatment can go ahead on a case-by-case basis.
Mitochondrial transfer will only be allowed when there is a "significant risk" of disability or serious illness.
Children born after mitochondrial transfer will not be entitled to discover the identity of the "third parent" donor.
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