LONDON (BBC) -- The revelations about Dr Hwang Woo-suk, South Korea's cloning and stem cell pioneer, have built into one of the biggest scientific scandals of recent memory.

Professor Hwang was a national hero in South Korea His fall from grace began with allegations about the practices he employed to procure eggs for his work.

He subsequently stepped down as professor at Seoul National University after an investigating panel said some of his landmark paper on custom stem cells was fabricated.

The fields of cloning and stem cell research could clearly have done without such revelations about one of its leading lights, given the controversy they already stoke. But how much impact has the retraction of Hwang's key scientific paper on custom stem cells had on research in the area?

"I don't think it has set back research, but clearly we weren't as far forward as we thought we were," says Jack Price, professor of developmental neurobiology at the Institute of Psychiatry in London.

Professor Peter Andrews, a stem cell expert at the University of Sheffield, broadly agrees: "Whether or not the cloning works has very little impact on most of the research going on into human embryonic stem cells," he told the BBC News website. "Most of the work on understanding the biology of these cells, how to use them, how to turn them into particular cell types for eventual applications, will come out of work on cell lines derived from surplus embryos not cloned ones."

Stem cells are the body's "master cells" and have the ability to produce all manner of tissues - which has led scientists to investigate their potential to be used to replace the cells that are missing or destroyed in conditions such as heart disease and diabetes.

Dr Hwang had enjoyed national hero status since 2004, when he announced that his research team had cloned 30 human embryos and had used them to produce stem cells that could one day help treat a range of diseases from diabetes to Alzheimer's.

In May 2005, Dr Hwang and his colleagues claimed to have used a cloning technique known as somatic cell nuclear transfer to make stem cells that were tailored to match individual patients.

But by November allegations had surfaced that the Seoul National University (SNU) professor used unacceptable practices to acquire eggs from human donors. Then, at the end of last year, researchers raised questions about Hwang's science.

Other groups have since produced cloned embryos An SNU team that had been investigating the South Korean researcher later reported there was no evidence that Professor Hwang's stem cells came from patient-specific clones.

Dr Hwang, however, has maintained that the science behind his work was sound, and that his country's scientists were still leading the field.

"I emphasize that patient-specific stem cells belong to South Korea and you are going to see this," he said in December.

From a biological standpoint, says Jack Price, there are no fundamental reasons why embryonic stem cells cannot be tailored to individual patients. So it should simply be a matter of time before a team repeats this scientific first.

But the efficiency with which such cell lines are made will determine whether such a technique can be of clinical use.