Can Kerry let the genie out of the test tube?

The Republican Party convention in New York last week was dominated by accusations about who was most fit to lead the US - President George Bush or his Democratic rival John Kerry. But while the campaigns of both parties have focused on such issues as homeland security and the war in Iraq, the controversial subject of stem cell research has also been moving up the political agenda.

The Republican Party convention in New York last week was dominated by accusations about who was most fit to lead the US - President George Bush or his Democratic rival John Kerry. But while the campaigns of both parties have focused on such issues as homeland security and the war in Iraq, the controversial subject of stem cell research has also been moving up the political agenda.

Senator Kerry suggested last month that he would remove restrictions on this area of medical research, reflecting recent opinion polls in the US which indicate it is gaining acceptance among Americans. This prompted the First Lady, Laura Bush, to defend her husband's hardline policy.

Stem cells represent the earliest stages in the development of the human body. As an embryo starts to develop in the womb, embryonic stem cells reproduce themselves to generate different types of tissue, from which all parts of the body form. Stem cells are also developed during adulthood (although in far smaller numbers than in embryos), replenishing ageing tissues with healthy cells.

Scientists want to research ways of manipulating stem cells in order to produce new body tissues that can replace diseased and damaged ones. They hope to use the technique to tackle diseases that attack the central nervous system, such as Parkinson's and Alzheimer's, as well as cancer and diabetes.

The science is controversial because to remove embryonic stem cells is to prevent the embryo growing into a human being. For this reason, it is strongly opposed by religious groups, who in America are traditional supporters of the Republican Party. There are also more general concerns that stem cells could be used for human cloning.

Government funding is vital for any non-commercial research, but in the US, none is available for scientists working with specially created stem cells. Limited federal funding is offered only for research on stem cells that have already been developed outside the laboratory, for example using cells left over from IVF programmes.

Dr Stephen Minger, director of the Stem Cell Biology Laboratory at King's College London, one of the leading stem cell research centres in the UK, says the US funding system is "schizophrenic".

"In the US, if you have the money, you can do anything you want," explains Dr Minger, himself an American. "There is no law restricting cloning, for example."

He adds that state law can also contravene federal law on funding, as has happened recently in California.

In the UK, there are fewer restrictions on stem cell research. In 2002, after a House of Lords committee gave the go-ahead for research using human embryos, the Government provided ?40m in funding. The UK Stem Cell Bank, the first of its kind in the world, opened in May. All stem cells used in government-approved tests must be stored at the bank.

Last month, scientists at Newcastle upon Tyne's Centre for Life were granted permission to create new stem cells from unfertilised eggs, the first such licence in the UK. The group, funded by the Government, last year became one of the first in Britain to take stem cells from spare IVF embryos, but the new licence has taken its work a stage further.

Alistair Balls, chief executive of the Centre for Life, admits the issue is still a sensitive one, and not just in the US. "The ethical debate strikes to the heart of the view of what life is and when it starts," he says. "But we are dealing with potential life here rather than life. We are using eggs that would be used in the IVF process. It's not lives that would otherwise have taken place. They would be discarded instead."

Pharmaceutical and biotech companies in the UK have not yet started investing heavily in stem cell research, and Mr Balls says he is happy that the public sector is funding and carrying out most of the initial work.

"It's very early days. We don't want to feel captive to commercial companies or allow them to decide areas where research takes place," he says.

King's College's Dr Minger adds that companies are themselves reluctant to get involved at such an early stage: "Big pharma is a bit nervous about stem cell research. But they are being very attentive to what's going on in the UK. Companies want something that is close to clinical trials. At the moment, it's a long way from commercialisation."

It is also too early to talk about a brain drain of frustrated US scientists and companies relocating to the UK to carry out stem cell research in a more liberal climate. But the warning signs are already there.

Debra Aronson, director of bio-ethics at the US Biotechnology Industry Association, says: "US scientists are already moving to the UK. Some are reluctant to invest their life's work in something that might become illegal."

Whether Kerry or Bush is in the White House, stem cells will remain a divisive issue in the US. And that can only be good news for Britain.