Scientists across the world have been researching a method called mitochondrial transfer, which extracts damaged cells from a mother's fertilised egg and replaces them with healthy cells from a female donor.
The process can prevent potentially fatal inherited genetic diseases, however church leaders have urged caution over technique - partly over safety concerns as the gene pool is changed and partly over ethical concerns that it could lead to specially bred "designer babies".
Last month UK scientists led by a team from the University of Newcastle announced the results of tests on more than 500 donated eggs that appeared to show the technique would lead to normal pregnancies.
However Spanish researchers at the CNIC research institute in Madrid found that the technique caused advanced ageing and changes in metabolism leading to obesity in mice.
Lead scientist Dr Jose Antonio Enriquez said the results highlighted the importance of avoiding a mismatch between mtDNA and nuclear DNA.
He said: "Just as with organ transplantation and blood transfusion, it is important to select mitochondrial donors, to ensure that the new mitochondrial DNA is genetically similar to that of the mother whose eggs require mitochondrial DNA replacement."
Having to find suitable mitochondrial DNA donors with a good enough genetic match would greatly complicate the business of applying the technology to families.
James Mildred, from CARE, told Premier: "This new research... is yet another example of why there were so many organisations including CARE who expressed very serious reservations about pursuing an ethically troubling new technique.
"Even though it's conducted on mice... it raises some really troubling questions.
"The very diseases that you're actually trying to prevent could actually be sparked by this technique."
Listen to Premier's Aaron James speaking to James Mildred: