MPs are voting on the amendment to the Human Fertilisation and Embryology Act 2008 because of a genetic technique which can cure some inherited diseases in babies.
The technique is called "mitochondrial DNA transfer". In it, the nucleus from the cell of an embryo or female egg is removed because its mitochondria - known as the "power packs" or "batteries" of the body cell - are faulty. The faults of the mitochondria cause some genetical diseases in children, such as muscular dystrophy.
This nucleus is then put in a female donor's egg with healthy mitochondria, technically giving the offspring three parents, specifically two mothers.
But Revd Dr Brandon McCarthy said: "The Archbishop's Council... does not feel that there has been sufficient scientific study or informed consultation into the ethics, safety and efficacy of mitochondria transfer.
"Without a clearer picture of the role mitochondria play in the transfer of hereditary characteristics, the Church does not feel it would be responsible to change the law at this time."
MPs are voting on whether to allow three-parent embryos this Tuesday. They've not been ordered to vote a certain way on the amendment; however the Daily Telegraph understands that the government's "made it clear to members to back the legislation."
60 MPs have already voiced opposition to the motion, including the Christian Conservative MP Fiona Bruce, who's expected to forward a motion calling for the vote to be delayed.
