Scientists at Newcastle University have created part-human, part-animal hybrid embryos for the first time in the UK, the BBC can reveal.
The embryos survived for up to three days and are part of medical research into a range of illnesses.
It comes a month before MPs are to debate the future of such research.
The Catholic Church describes it as "monstrous". But medical bodies and patient groups say such research is vital for our understanding of disease.
They argue that the work could pave the way for new treatments for conditions such as Parkinson's and Alzheimer's. - BBC News