Scientists have condemned a leading Catholic cardinal's calls for those who carry out embryonic stem cell research to be excommunicated.
Scientists say it is ethical to use embryonic stem cells
Vatican-based Cardinal Alfonso Lopez Trujillo told a Catholic magazine such research was "the same as abortion".
He said excommunication should apply to "all women, doctors and researchers who eliminate embryos".
Scientists in the UK called his comments outrageous and said they amounted to "religious persecution".
Cardinal Trujillo, head of the Vatican's Pontifical Council for the Family, will open the church's World Meeting of Families in Valencia, Spain, on Saturday.
He told Famiglia Cristiana magazine: "Destroying an embryo is the equivalent of abortion.
"Even talking about the defence of life and family rights is being treated as a sort of crime against the state in some countries - a form of social disobedience or discrimination against women."
'God will judge'
But Dr Stephen Minger, leading stem cell expert at Kings College London, said: "Having been raised a Catholic, I found this stance really outrageous.
"Are they going to excommunicate IVF doctors, nurses and embryologists who routinely put millions of embryos down the sink every year throughout the world?
"It is more ethical to use embryos that are going to be destroyed anyway for the general benefit of mankind than simply putting them down the sink."
Professor Allan Templeton, president of the Royal College of Obstetricians and Gynaecologists, in London, called the cardinal's comments "insensitive and unhelpful".
He added: "I cannot really believe it represents the thinking of the Roman Catholic church."
Professor Julian Savulescu, uehiro chair in practical ethics at the University of Oxford, warned: "This amounts to religious persecution of scientists which has no place in modern liberal societies.
"Presumably God will be the one to judge the scientists, not Church leaders."