Paul Murphy, the Welsh Secretary, may resign from the Cabinet over Gordon Brown's refusal to offer MPs a free vote over a new law to allow more experiments on embryos.
His resignation would be embarrassing for Mr Brown, since he recalled Mr Murphy only two months ago to replace Peter Hain, who quit after late declarations of more than £100,000 in donations to his Labour deputy leadership campaign last year.
Mr Murphy is among a group of Catholic ministers who want to vote against the Human Fertilisation and Embryology Bill, which would allow the creation of human-animal hybrid embryos for scientific research. Others include Ruth Kelly, the Transport Secretary, and Des Browne, the Defence Secretary.
The Government has offered Labour MPs the chance to abstain if they write to party whips asking to be excused on religious or ethical grounds. But ministers who vote against would almost certainly have to resign or be sacked.
Supporters of the Bill believe hybrid embryos could pave the way for cures for diseases such as multiple sclerosis and Alzheimer's. But the pressure on Mr Brown to join the Tories and Liberal Democrats in allowing a free vote grew yesterday when the leader of the Catholic Church in Scotland urged ministers to resign so they could oppose the proposal.
In his Easter sermon tomorrow, Cardinal Keith O'Brien will say: "We are about to have a public government endorsement of experiments of Frankenstein proportions. This Bill represents a monstrous attack on human rights, human dignity and human life ... The Government has no mandate for these changes: they were not in any election manifesto, nor do they enjoy public support."
The Department of Health said: "This is not about 'creating monsters'. It is purely laboratory research, and is aimed at increasing knowledge about serious diseases and treatments for them."
A spokesman added that it was proposing "strict controls" on the research which were broadly the same as those applying to human embryos.Reuse content