Scientists have made a breakthrough in producing stem cells from cloned human embryos. Researchers in South Korea said that they had for the first time produced cells tailored for an individual patient.

The team produced 31 cloned human embryos by transferring the nucleus from the skin cell of a patient into an egg - taken from a donor - that had its own nucleus removed.

Professor Woo Suk Hwang of Seoul National University, who led the research, said that 18 women donated 185 eggs for the research and 11 patients aged between the ages of two and 56 gave samples of their skin. From the resulting 31 cloned embryos, the researchers cultured 11 separate "lines" of embryonic stem cells which divided continuously in the laboratory.

The study, published in the journal Science, builds on research last year that resulted in the world's first cloned human embryo. It could lead to effective treatments for a range of devastating conditions, such as Parkinson's disease, spinal cord injuries and diabetes, and might even result in an end to organ transplants.

"This report brings science a giant step forward towards the day when some of humankind's most devastating diseases and injuries can be effectively treated through the use of therapeutic stem cells," Professor Hwang said yesterday in London.

However, critics argued that the development brought closer the possibility of producing a cloned baby using the same technique, a procedure banned in Britain.

The South Korean scientists emphasised this was not their aim. They instead demonstrated for the first time that the "therapeutic cloning" technique is feasible for both men and women and for the young as well as the old and that the donated egg does not have to come from the patient or even someone related to the patient.

Professor Gerald Schatten of the University of Pittsburgh School of Medicine, the only non-Korean member of the team, described the breakthrough as a huge leap forward in the understanding and development of stem cell therapies.

"What the study shows is that stem cells can be made that are specific to patients regardless of age or sex and that these cells are identical genetic matches to the donor," Professor Schatten said.

"If they can be safely used in transplant, the promise for effective treatment - perhaps even cure - of devastating diseases and injuries comes with- in reach," the professor said.

Other scientists described the findings as remarkable.

Anne McLaren, a distinguished embryologist at Cambridge University, said that the potential for deriving unlimited quantities of embryonic stem cells from patients with chronic diseases promises to revolutionise clinical research into these disorders.

"Some thought that Hwang's success with cloning only worked because it used a woman's egg and the somatic cells surrounding it. But now, good news for men. Some of the cloned lines were derived from men's skin cells," Dr McLaren said.

Professor Ian Wilmut of the Roslin Institute in Edinburgh, who pioneered the cloning technique used by the South Koreans in producing the sheep Dolly, congratulated the team on its results.

"These new observations make a very significant and important step forward toward the use of cells from cloned human embryosfor research and therapy," Professor Wilmut said.

Life, the anti-abortion charity, however, denounced the research, saying that it brought reproductive cloning a step closer and exploited the young women who would be used as egg donors for such research.

"This news from South Korea makes reproductive cloning a clear and present global danger. If, as they claim, these South Korean scientists can reliably produce cloned embryos healthy enough to survive to the blastocyst stage for cell harvesting, we can assume that they can reliably produce embryos healthy enough to try implanting them in women," a spokeswoman said.

"This Frankenstein science should be banned in every civilised country. Cloning involves exposing women to dangerous fertility drugs in order to collect sufficient eggs to use in the cloning process. It is unsafe and inefficient," she added.