THE Republican matriarchs Laura Bush and Nancy Reagan have taken up arms on opposing sides of a fiery debate on stem cell research, bringing a battle that had hitherto been waged largely on the pages of scientific journals into mainstream politics.

The research is opposed by American conservatives because it sometimes uses human embryos.

Mrs Bush criticised supporters of the research, who include Mrs Reagan and her son Ron, for apparently overstating the benefits that could be drawn for sufferers of diseases such as Alzheimer’s. Mrs Reagan’s husband, the former President Ronald Reagan, suffered from Alzheimer’s disease until his death in June.

Mrs Bush said the “implication that cures for Alzheimer’s are around the corner is just not right and it’s really not fair to people who are watching a loved one suffer with this disease”.

It was far from clear, she said, that this “very, very preliminary” research could cure diseases such as Alzheimer’s.

Stem cells can change into any body tissue and, it is thought, can be used to grow healthy tissue to replace diseased cells.

Mrs Bush insisted she was not singling out the Reagans as she defended restrictions placed on the research by her husband, the President.

Ron Reagan, the dead former President’s son, caused uproar in some conservative circles by speaking in favour of the research at the Democratic nominating convention last month. His mother also paid tribute to the research at her husband’s funeral.

Mrs Reagan first took on Mr Bush’s policy on stem cells publicly in May, shortly before her husband’s death.

“We have lost so much time already. I just really can’t bear to lose any more,” she said, in a thinly veiled reference to Mr Bush’s decision three years ago to restrict stem cell research in most cases.

Scientists say that the President has severely hampered progress in the US, and sparked a brain drain abroad, including to Britain, where researchers at Newcastle University announced yesterday that they had been given permission to create embryos as a source of stem cells.

The issue is divisive in America, where the vocal lobby of abortion opponents objects to the use of embryos for research.

Stem cell “lines” can be created from a single, frozen embryo generated by an unused egg at a fertility clinic.

The ethical argument centres on whether this embryo constitutes a human life. Some scientists argue that stem cell research could be successful just using adult cells, from umbilical cords, for example. Others say that this would hamper progress.

Proponents of using embryos say it will dramatically increase the odds that they will cure a variety of diseases if they are free to create as many “lines” as necessary, with public funding.

The issue has attracted famous potential beneficiaries of the research, including the actors Michael J. Fox, who has Parkinson’s disease, and Christopher Reeve, who is paralysed.

Mrs Reagan and her son find themselves on the same side of the debate as John Kerry. The Democratic nominee has sought to gain advantage from an issue that divides Republicans by accusing his opponent of banning stem cell research and inviting Ron Reagan to speak out in favour of the work at his party’s convention.

Mrs Bush said it was “ridiculous” to suggest that her husband had banned stem cell research. But Mr Kerry’s spokesman said the restrictions applied to 99.9 per cent of potential stem cell lines.

“If that’s not a ban,” he said, “we don’t know what is.”

Mrs Bush drew scorn from some in the stem cell research community with her remarks.

Lawrence Goldstein, a scientist at the University of California and stem cell expert, said the research could bring benefits for patients in as few as two or three years, and probably within 20 years. The First Lady was “dead wrong,” he said.

“I respect her moral position,” he told The Times yesterday. “But she doesn’t know what she’s talking about. I sincerely doubt she has educated herself on this, and I have the same problem with the President’s position.”

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