The Bishop of Oxford has refused to condemn the actions of a British couple planning to have a 'designer' baby to help save the life of their son.

But, speaking on the Today programme on BBC Radio 4, he said the new baby must be wanted for itself and not just as a way of getting a genetic match.

Leeds couple Raj and Shahana Hashmi want a baby who will be a genetic match for their son Zain, three. He has a potentially fatal blood disorder and only a compatible bone marrow transplant can save him.

The couple have been given the go-ahead by the Human Fertilisation and Embryology Authority to have their IVF embryos screened to get a genetic match.

Mr Hashmi said: "This baby is going to be a special gift from nature, not a designer baby. We are not destroying anything -- not hurting anybody."

The embryo selection will enable cells from the baby's umbilical cord to be used for the transplant to save Zain's life.

The Bishop of Oxford said the practice should be done only on a case by case basis.

He said: "I think a very clear distinction can be made between preventing disease as in this case and enhancing ordinary qualities in other circumstances.

"It's very important that the child is wanted for its own sake.

"It would be very sad and damaging if the child grew up knowing it had been brought into the world only in order to provide blood for the sibling."

Zain has beta thalassaemia major, a condition which creates fatal levels of iron in his blood.