Parliament is expected to debate a draft bill later this year that would allow scientists to create hybrid embryos for research as long as they are destroyed within two weeks.
Ministers say the creation of animal-human embryos - created by injecting animal cells or DNA into human embryos or human cells into animal eggs - will be heavily regulated.
They insist that the Human Tissue and Embryo Bill would make it illegal to implant “chimeras” - named after the mythical creature that was half man and half animal - into a woman’s womb.
The bill would allow the screening of embryos for genetic or chromosomal abnormalities that might lead to serious medical conditions, disabilities, or miscarriage. It would also permit doctors to check whether an embryo could provide a suitable tissue match for a sibling suffering from a life-threatening illness.
The bill would abolish the requirement for fertility clinics to consider the need for a father when deciding on treatment, which means clinics would no longer be able to deny treatment to lesbians and single mothers.
The Catholic bishops of England and Wales said most of the procedures covered by the bill “should not be licensed under any circumstances” because they violate human rights.
But, in a submission to the Parliamentary joint committee scrutinizing the draft legislation, they added that they are anxious to limit the destruction of hybrid embryos — even if it is “interspecies” — once they have been brought into existence.
In their submission, the bishops said “embryos with a preponderance of human genes should be assumed to be embryonic human beings, and should be treated accordingly.”
The bishops argued that the genetic mothers of “chimeras” should be able to carry them to term and raise them as their own children if they wished.
“In particular, it should not be a crime to transfer them, or other human embryos, to the body of the woman providing the ovum, in cases where a human ovum has been used to create them,” the bishops wrote.
“Such a woman is the genetic mother, or partial mother, of the embryo; should she … wish to carry her child to term, she should not be prevented from doing so.”