Pro-lifers have expressed alarm after scientists created dozens of human embryos with three genetic parents.
Researchers at Newcastle University used embryos originally donated for IVF to create the new embryos, but these were destroyed within a matter of days to comply with fertility laws.
The experiments are designed to help women suffering genetic problems affecting their eggs, which can cause their children to die soon after birth.
But concerns have been raised that the experiment completely distorts the “natural process”, and that the research may not actually help women.
Pro-life campaigner Josephine Quintavalle, from Comment on Reproductive Ethics (CORE), warned that the consequences of such experiments are unknown.
And a Department of Health spokesman stressed there are “serious ethical considerations” involved before the experiments are extended.
Scientists want to use the process to combat genetic problems affecting the mitochondria – the ‘batteries’ inside all cells that create energy for the whole body to function.
The scientists started by taking a one-day-old human embryo from a mother with malfunctioning mitochondria, and extracted the inner part of the cell which contains most of the DNA.
Then they took another one-day-old human embryo from a second, donor mother.
This was then stripped of almost all of its DNA, by destroying its inner part, leaving just the egg shell containing its healthy mitochondria ‘batteries’.
These two elements were combined with the healthy DNA from the natural mother and father and placed in the donor’s egg to create a new human embryo.
This meant the scientists had created an embryo with three genetic parents.
Mrs Quintavalle, from CORE, said: “We have no clue what the long-term consequences will be”, and commented: “In terms of experiments this is the worst that anyone has come up with.”
Under rules laid down by the Human Fertilisation and Embryology Authority (HFEA), the embryos had to be destroyed after around six days.
Faults in the mitochondria can cause around 150 known diseases and affect around one in every 6,500 people.
The controversial Human Fertilisation and Embryology Act 2008 allows for regulations to be passed which would mean embryos created in this way could be brought to term.
A spokesman for the Department of Health said: “In addition to issues of safety and efficacy, there are serious ethical considerations to be taken into account.
“Any proposed regulations would be subject to significant public consultation and Parliamentary debate before they could become law.”