Pro-life campaigners have criticised a Bicester couple for pushing the boundaries of science too far as their hopes of a 'designer baby' moved a step closer.

Julie du Plessis, education officer for the charity Life, said: "Children should not be created in order to serve the medical needs of older siblings. We are creating an industry where children are made to order, bought and sold."

Michelle Whitaker, 30, and her husband Jayson, 32, of Isis Avenue, Bicester, sought treatment in the USA after the Human Fertilisation and Embryology Authority refused to approve a licence to allow tissue typing IVF to provide a match for their four-year-old son, Charlie, who suffers from a rare blood disorder, Diamond Blackfan Anaemia.

Two embryos have now been successfully implanted in Mrs Whitaker's womb after IVF treatment at the Reproductive Genetics Institute in Chicago.

Doctors have said Charlie's best hope is a transplant of primitive stem cells from a sibling sharing the same immune system genes.

His illness, which affects about 50 children in Britain, requires him to have blood transfusions every three weeks and stomach injections five times a week.

Nine eggs were fertilised using Mr Whitaker's sperm.

Three were a match for Charlie, but only two of these were selected for implantation.

Fertility specialists said the embryos had thrived well and there was a 50 per cent chance of a successful pregnancy -- more than double that of a normal IVF procedure.

Mrs Whitaker said: "I am hopeful about the implantation being a success, and we have been told the embryos are thriving so well that we could have twins."