An attempt to stop scientific research into human-animal "hybrid" embryos has failed in the House of Lords.
Hybrids are made using an animal egg mixed with human genes
Critics say the development is unnecessary and morally wrong, but they were defeated by a margin of more than two to one by peers.
Ministers say hybrid embryos are vital for research into life-threatening and debilitating diseases.
Under government-backed plans, the embryos will be kept alive for 14 days but not implanted into a womb.
A proposed amendment to the Human Fertilisation and Embryology Bill, to prohibit the creation of inter-species embryos - known as human admixed embryos - was defeated by 268 votes to 96, a majority of 172.
The embryos contain a small amount of animal DNA.
Lord Alton of Liverpool, who proposed the ban, told peers: "We are being invited to cross a Rubicon."
He claimed scientists would soon no longer need to use stem cells from embryos to carry out research.
But Labour peer and fertility scientist Lord Winston said: "Ninety-five per cent of the scientific fraternity believe that embryonic stem cell research is necessary."
Health minister Lord Darzi said it was necessary to use animal eggs to create embryos for research because of "the shortage of human eggs".
He added: "Such research will only be permissible with a licence from the HFEA (Human Fertilisation and Embryology Authority) and only in circumstances where the HFEA deemed the research necessary.
Ethics and technology
"In making such decisions the HFEA will be required to take into account all other avenues of research which may achieve the same end."
Tory former cabinet minister Lord Tebbit said: "These are matters that are more of ethics than of technology. Because something is scientifically possible does not mean that it should be done.
"Because it might bring great benefits to particular people does not mean it should be done.
"If we accept arguments of that kind we are effectively saying that the end justifies the means."
The Archbishop of Canterbury, Rowan Williams, earlier criticised the bill's "instrumental" view of humanity.
Liberal Democrat MP Evan Harris, who has campaigned for the easing of restrictions on research, said: "The science and ethical arguments won the day as it is not rational for the human early embryos to be permitted in regulated research but not to permit part-human embryos to be used."
He added: "This is good news for scientists and good news for patients, for whom there is some hope of new treatments from embryo research