British MPs effectively gave the go-ahead Monday for human-animal embryos to be used in scientific research.

They blocked a bill which would have banned the creation of inter-species embryos by a vote of 336 to 176.

Critics had argued that creating human-animal embryos would be a "step too far" and ethically questionable -- some going so far as to brand the technique "Frankenstein science."

But Prime Minister Gordon Brown told a British newspaper that such cutting edge research could "bring new cures and treatments to millions of people."

The vote on "admixed" embryos -- which transfer human cell nuclei into animal eggs -- was part of a larger review of embryonic science laws which have not been updated in about two decades. The embryos will not be allowed to develop for more than two weeks.

Other proposals could overhaul Britain's abortion laws and allow easier access to fertility treatment for lesbians. One measure would also deal with so-called "saviour siblings."

Saviour siblings are children born through in-vitro fertilization from selected embryos. The embryos are chosen specifically because they have tissue that could help a sibling suffering from a genetic disease.

Brown said admixed embryos are a "moral" issue because they could help scientists improve the lives of patients with such diseases as Parkinson's and Alzheimer's.

Opponents of human-animal embryos and saviour siblings include clergy, particularly in the Catholic Church. Church leaders have said such research sets scientists and society on a dangerous moral course.

Meanwhile, the science watchdog group Human Genetics Alert says new laws facilitating admixed embryos are a slippery slope towards the creation of designer babies.

"Once we start down the road to human genetic modification, it will be very difficult to turn back," the group wrote in a briefing paper.

With files from The Associated Press