A cross-party attempt to ban the use of hybrid human-animal embryos for scientific research was rejected by the Commons tonight. MPs voted 336 to 176 (a majority of 160) against the move led by Tory former minister Edward Leigh.
The Commons then rejected a cross-party bid to ban the use of so called "true hybrids" using the sex cells of a human and an animal. Voting was 286 to 223, majority 63.
It was the first in a series of critical votes on emotive issues in committee stage debate on the Human Fertilisation and Embryology Bill - the biggest shake-up of law in this area for 20 years.
Mr Leigh (Gainsborough) said the use of "admixed" embryos, using genetic material from both humans and animals, would cross an "entirely new ethical boundary," and turn the UK into a scientific "rogue state".
The embryos created would have to be destroyed after 14 days, but scientists hope stem cells can be harvested and used to create brain, skin, heart and other tissue for treating diseases.
Mr Leigh warned it was a "step too far" adding: "In many ways we are like children playing with landmines without any concept of the dangers of the technology that we are handling."
But Labour's Chris Bryant (Rhondda), a former Anglican curate, compared Mr Leigh's arguments to those used by church leaders against the smallpox vaccine.
"They were wrong and I think you are wrong today," Mr Bryant said.
All the main parties have allowed MPs a free vote on the creation of the "admixed" embryos and on the next issue to be debated tonight - the creation of so-called "saviour siblings" whose genetic material could help sick relatives.
Controversial attempts to reduce the abortion time limit will be debated tomorrow.
For the Tories, Mark Simmonds said he did not agree that admix embryos showed no prospect of providing solutions to the "very real problems that exist" to find cures for debilitating diseases.
But he raised concerns about the creation of "true hybrids", warning that the scientific community had expressed "serious reservations" about hybrids that weren't always at the "human end of the spectrum".
Mr Simmonds accused the Government of "shifting" its position on true hybrids, adding: "This seems to undermine any consistent ethical position surrounding admixed embryos."
Lib Dem spokesman Evan Harris, a doctor, said his conscience told him to back the Bill.
And he took issue with claims it was a radical departure from the ethical principles in the Human Fertilisation and Embryology Act 1990.
"The same principles in the 1990 Act apply in this Bill. Embryo research will still be heavily regulated in at least five ways."
Health Minister Dawn Primarolo said the shortage of human eggs presented a "significant barrier" to embryonic stem cell research and experts believe hybrid embryos were a "pragmatic" solution to the problem.
She assured MPs: "Any licence application to create a human admix embryo for research will need to prove to the HFEA that the proposed use of the embryo is necessary.
"Not simply that they want to try it as scientists, but that it is necessary and no other route of research will enable the development of the science to understand the development of the treatment."
Tory leader David Cameron confirmed earlier today that he backed proposals for the creation of human-animal hybrid embryos for medical research as well as so-called "saviour siblings" selected by parents in order to provide tissue material for seriously ill children.
Yesterday, the Prime Minister also voiced his support, hailing new ground-breaking techniques as "an inherently moral endeavour" which could save millions of lives.