Regulatory agencies will be needed to oversee the use of stem cells when current experimental therapies are ready to be tested in humans, scientists said on Tuesday.
They told a meeting on the ethical, legal and social issues surrounding stem cell research that the potential new treatments for illnesses ranging from heart disease and diabetes to Alzheimer's and Parkinson's are still 5 to 15 years away.
But how stem cell therapy will be used in humans and its safety and therapeutic benefits must be looked at very carefully.
"You need to have regulation that is appropriate," said Dr Stephen Minger, a leading stem cell researcher at King's College London.
"It needs to be assessed rigorously long before we go into human patients simply because it is an unproven technology and we have no experience putting these cells into patients," he added.
Professor Martin Evans, of the University of Cardiff in Wales said an international, rather than local or national agencies, may be needed.
Stem cells are master cells in the body that can develop into any cell type. Scientists believe they could act as a type of repair system for the body.
But their use is controversial because the most promising stem cells for treating human diseases are derived from very early human embryos left over from fertility treatments.
Embryonic stem cell research involves the destruction of embryos. In the United States, federal funds for experiments using embryonic stem cells are restricted.
Professor Jan Helge Solbakk, of the University of Oslo in Norway, told the meeting of researchers, patient groups and policy makers that countries which allow fertility treatments but ban embryonic stem cell research should export their spare embryos to nations that do.
"My message to these countries ... is that one cannot continue to ban this research while at the same time silently accepting it will import any future therapies. That is a kind of double standard," said Solbakk.
Minger said he supported Solbakk's suggestion.
"Embryos are in short supply. That is one of the major stumbling blocks in the research," he added.
The sourcing of donated embryos and eggs to create cloned human embryos for stem cell research is a sensitive issue.
Professor Kwang Woo-suk, the scientist at Seoul National University in South Korea who created stem cells with a patient's specific genetic material from cloned embryos, said on Monday his work met government guidelines on ethics.
His comments followed US newspaper reports saying a US scientist suspended collaboration with him over rumours that he had used eggs in the ground-breaking research from a junior scientist in his lab.
Professor Peter Braude, of King's College London, said sourcing of donated eggs for stem cell research poses questions of supply and ethics that need to be addressed.