After hours of anguished debate over the ethics and science behind embryonic research, they decided to back the use of hybrid embryos in the search for medical cures and greater understanding of serious illnesses and allow parents of children suffering serious diseases to use in-vitro fertilisation to select "saviour siblings" who can act as donors for transplants to save their sick brothers and sisters.
A proposed ban on hybrid embryos was voted down by 336 to 176, as the substantive part of the Human Fertilisation and Embryology Bill sailed through the Commons. It will make Britain one of the few countries that regulates and sanctions the use of hybrid, or "admix", embryos and could also provide a boost to the bioscience industry in research centres such as at Edinburgh University.
Three Cabinet ministers voted against the use of hybrid embryos: Des Browne, the Defence and Scottish Secretary; Ruth Kelly, the Transport Secretary and Paul Murphy, the Welsh Secretary. The majority of the shadow cabinet – including shadow foreign secretary William Hague and shadow home secretary David Davis – also backed the ban, even though David Cameron, the Conservative Party leader, voted against.
Religious leaders say hybrid embryos threaten the sanctity of human life and their efficacy in research is unproven. Many MPs disputed Gordon Brown's claims that the development of hybrid embryos was a "moral endeavour" that would potentially save millions of lives.
All the opposition parties have been given a free vote on the entire Human Fertilisation and Embryology Bill, while Labour MPs have free votes only on four areas: human-animal hybrids; the creation of saviour siblings; the access to a father figure when considering a woman for fertility treatment and the time-limit on abortion.
Last night, the main debate was around the issue of "admix" embryos, where the nuclei of human cells are inserted into animal eggs and kept alive for up to 14 days for research.
Edward Leigh, the Tory MP who introduced an amendment to ban hybrid embryos, argued that there was "no evidence yet to substantiate" claims this may lead to treatment for Parkinson's and Alzheimer's.
Mr Leigh, a former minister, said: "We do not believe that regulation is enough. We believe this is a step too far and, therefore, should be banned.
"In embryos, we do have the genetic make-up of a complete human being and we could not, and should not, be spliced together with the animal kingdom." He added: "I believe that science is doing wonderful things, but it can also do terrible things. I do think Science should be our servant and not our master."
The debate cut across party lines. , with some MPs allowed a free vote on the matter after heaping pressure on Gordon Brown Sir Gerald Kaufman, a former Labour minister, also opposed the hybrid embryo research, saying: "How far do you go? Where do you stop? What are the limits and what are the boundaries? If you permit the creation of hybrid embryos now, what will you seek to permit next time, even if you have no idea where it will lead?"
But Chris Bryant, the Labour MP for Rhondda and a former Anglican curate, compared Mr Leigh's arguments with those used by church leaders against the smallpox vaccine.
"They were wrong, and I think you are wrong today," he said.
Critics of the legislation have branded it "Frankenstein science," and Mr Leigh quoted from the Mary Shelley classic.
"If an embryo could talk, perhaps it would echo what Mary Shelley did say in Frankenstein: 'I, the miserable and the abandoned, am an abortion to be spurned at and kicked and trampled on'."
Labour's Ian Gibson, a former cancer researcher, said his support for the bill had been "fired up" by letters from constituents grappling with illnesses. He said scientists should be encouraged to "try everything".
He told the Commons said: "I would be the last person to prevent our scientific and medical community trying to develop the kind of cures that help people."
Research holds key to treatments
WE WELCOME the passage of this bill. It would enable the development of embryonic stem cell research to progress and, over time, it has the potential to benefit people with dementia and their carers.
Hybrid embryos are important. We still need to do a lot of experimentation to understand how stem cells develop and the conditions in which they can grow.
In the short term, there are not enough adult stem cells to do this research on the scale required. At the moment, adult stem cells come from fertility treatment, umbilical cord material or new experimental techniques that do not use embryos but are still in an early experimental phase.
There are not enough to go around, so hybrid embryos are the next best thing.
What is crucial to understand is that these embryos are not likely to be used for treatment. They will hopefully lead to better understanding of how stem cells work which, in turn, makes the discovery of therapies more likely. They are not going to be implanted in patients.
It's a discovery curve and there are no guarantees about which way the science will go. We have got to have access to new techniques and this is one well worth exploring.
Jim Jackson is chief executive of Alzheimer Scotland.
Unethical work which blurs nature's boundaries
THE decision to support animal-human hybrid embryology is both unnecessary and unethical.
By caving into pressure from the biotechnology industry, the government has patronisingly dismissed major moral and ethical concerns.
Research published last year after the bill was printed shows that skin cells can be reprogrammed to have all the potential of embryonic stem cells. These induced pluripotent stem cells make any need for hybrid embryos redundant.
We believe the work is also unethical because it blurs established boundaries in nature. As Christians, we recognise that humans are made in the image of God and should not be blasphemed against in this way.
There is less agreement on the exact meaning of those terms, but most Christians agree it at least implies that humans are, in some sense, special and distinct from other parts of creation.
We also uphold the biblical prohibition of the unlawful mixing of "kinds". In the biblical perspective, species integrity is ultimately defined by God rather than by physical features. The fusion of human and non-human genomes may therefore be perceived as running counter to the sacredness of human life and humanity created in the image of God.
While biology perhaps does not give us clear enough boundaries to justify a prohibition, concepts arising from a Christian view of humanity certainly do.
If the world's scientific community decided not to pursue this particular direction of research, then new avenues would almost certainly open up and lead to alternative modes of finding cures and treatments.
Dr Andrew Fergusson is communications director for Christian Medical Fellowship.