British plans to allow scientists to use hybrid animal-human embryos for stem cell research won final approval Wednesday in a sweeping overhaul of sensitive science laws.
The House of Commons also clarified laws that allow the screening of embryos to produce babies with suitable bone marrow or other material for transplant to sick siblings.
It was the first review of embryo science in Britain in almost 20 years.
The legislators voted 355-129 to authorize the proposals after months of sometimes bitter debate that pitted Prime Minister Gordon Brown's government and scientists against religious leaders, antiabortion campaigners and others anxious about medical advances.
Brown says he believes scientists seeking to use mixed animal-human embryos for stem cell research into diseases such as Parkinson's will help improve - and save - millions of lives.
Decisions by Britain's Human Fertilization and Embryology Authority, an independent body that regulates fertility and embryo research, to allow the practice have previously been vulnerable to challenges in court.
While Britain has been seen as a world leader in stem cell and cloning research, similar work to create human embryos from animal eggs is being conducted in China and the United States.
British lawmakers had already endorsed individual proposals, but Wednesday's vote involved the complete draft bill.
Britain's government opted not to allow legislators to use the debate to reconsider abortion laws, last drafted in 1990.