South Korea's top human cloning scientist Hwang Woo-suk has apologised and resigned after his colleagues announced that he had fabricated results in his stem-cell research.
Dr Hwang has been hailed as a hero in South Korea
Several UK-based experts in the field have reacted to the news.
PROF COLIN MCGUCKIN :: Regenerative Medicine, University of Newcastle
Scientific integrity is everything. The rush to cure disease with stem cells has moved too fast and superstar embryonic scientists are appearing in many countries.
The sad reality however, is that this science is not easy and embryonic stem cells are not going to regularly treat patients for many years.
The hype surrounding embryonic stem cells has also overshadowed the fact that other stem cell treatments - including from umbilical cord blood - are a more likely alternative - and governments should sit up and take note that pouring money into embryonics is unlikely to bring cost effective treatments to the health service in the short term.
Korean science however, should not be denounced, since Dr Hwang alone did not represent Korean stem cell research, and other good work is being carried out there.
PROF PETER ANDREWS :: Stem Cell Expert, Sheffield University
This really is sad news.
I am sure that eventually cloning will prove feasible, but, if the reports are accurate, it is sad that someone apparently felt the need to claim results that they had not yet achieved!
In the end the progress of science depends on results being repeated in independent labs, but along the way we have to work by trusting our colleagues.
It comes as a shock when occasionally we find that someone has betrayed that trust.
DR HUSEYIN MEHMET :: Weston Senior Lecturer in Neurobiology, Imperial College London
I think the news of Dr Hwang's resignation represents a sad day for stem cell research.
He was one of the most respected scientists in the field and we are all devastated that he has allegedly felt the need to fabricate data.
The integrity of scientists is of paramount importance in medical research. This sad outcome illustrates the pressure on scientists to publish their work and put findings into the clinic, sometimes prematurely.
On the other hand, this was a technical breakthrough and the early detection of the misconduct means that scientifically the field of stem cell research has not been fatally damaged.
PROF JACK PRICE :: Centre for the Cellular Basis of Behaviour, MRC Centre for Neurodegeneration Research, Institute of Psychiatry, London
This is very disappointing news.
I guess we should have been suspicious given the speed with which he overcame problems that were holding back other labs - I guess in the end the pressure to succeed was too great.
So much had been invested in him by the state. This is a spectacular collapse.
PROF MALCOLM ALISON :: Centre for Diabetes and Metabolic Medicine, Institute for Cell and Molecular Science, London
He is in trouble on two counts, firstly the oocytes (eggs) were donated from his own female staff (apparently without his knowledge), and we know there must be no financial inducement or other pressures put to bear on potential donors.
Secondly, he claims that 11 cell lines were made from 11 patients, a colleague claims there were only two cell lines and that the other nine were faked by electronic manipulation of photographs.
If found guilty, Dr Hwang is completely washed up, a scientist's credibility relies on his integrity.
It's astonishing that he acquired £23m ($40m) in government funding in recent times, demonstrating the commitment of the Korean government to stem cell research.
PROF DAME JULIA POLAK :: Director, Tissue Engineering and Regenerative Medicine Centre Investigative Science, Imperial College London
If this is true, this type of malpractice does not help to advance stem cell research.
Most of researches in the field adhere very high scientific, moral and ethical standards.
DR AINSLEY NEWSON :: Researcher in Medical Ethics, Imperial College London
Research fraud is a very serious matter in any scientific discipline. That it seems to have occurred in this already controversial area of research is doubly unfortunate.
But Dr Hwang's alleged conduct does not mean that all embryonic stem cell research is unethical.
We must continue to debate the promises and pitfalls of this important area of medicine.