"Designer babies" are children selected while still in embryonic form in order to provide healthy cells to save the life of a seriously ill sibling, the Telegraph newspaper reported.
Opponents say that the selection of only healthy embryos that match the tissue type of a sibling will lead to the creation of babies to provide "spare parts."
Among the opponents is Lord Winston, the fertility expert who helped to develop the technique of pre-implantation genetic diagnosis (PGD), which allows embryo selection.
The authority´s decision Wednesday went "too far," said Lord Winston. "I fear that it is treating the offspring to be born as a commodity."
Lord Winston asked how parents would regard the child if the technique failed. He also questioned whether it was fair to subject a child to a lifetime of donating cells to a sibling.
The decision by the Human Fertilization and Embryology Authority could allow a couple at risk of passing on a genetic disease to use PGD, not only to select embryos free from the disease, which is at present allowed, but also to select an embryo so that stem cells from the resulting baby´s umbilical cord blood could be used in the treatment of an existing sibling.
An application has already been made to the authority by Dr. Simon Fishel, the scientific director of the Park Hospital, Nottingham. He wants to select an embryonic sibling to save the life of Zain Hashmi, who has a potentially fatal blood disorder.
A bone marrow transplant is the only treatment, but neither of Zain´s parents nor their other four children are a match.
If his application is approved, Fishel aims to create a number of embryos using in vitro fertilization methods. PGD involves the removal of a cell from an embryo for tests to see whether the embryo carries a genetic disorder.
The Catholic Church condemns in vitro fertilization and related practices.
John Paul II in his encyclical "Evangelium Vitae," No. 14, warns about artificial reproduction, noting: "The number of embryos produced is often greater than that needed for implantation in the woman´s womb, and these so-called ´spare embryos´ are then destroyed or used for research which, under the pretext of scientific or medical progress, in fact reduces human life to the level of simple ´biological material´ to be freely disposed of."