Two of the most prominent figures in the pioneering field of stem-cell research have rocked their tight-knit community of scientists by dramatically falling out over suggestions that payments were made for human eggs and that junior female scientists may have felt pressured to become egg donors.

Professor Gerald Schatten of Pittsburgh University School of Medicine in Pennsylvania said that he will no longer collaborate with Professor Woo-Suk Hwang of Seoul National University in South Korea who led the team that cloned the first human embryo.

Professor Schatten accuses Professor Hwang of misleading him about the source of the human eggs used in pioneering experiments that led to the formation of the first human stem cells from embryos cloned in South Korea.

Professor Hwang has vehemently denied allegations that the eggs used in his experiments were paid for or that some of the donors involved were junior members of his own team.

The acrimony is all the more surprising because both men had been almost sycophantically effusive about each other's contribution to their joint effort until Professor Schatten issued a damning statement through his university.

"Information came to my attention suggesting that misrepresentations might have occurred relating to those oocyte [egg] donations."

"I have accordingly suspended my collaboration with Professor Hwang," said Professor Schatten, who refused to elaborate further.

The two scientists began collaborating in 1984, after Professor Hwang had published his pioneering research in the journal Science which unveiled the first cloned human embryo.

Professor Hwang has always maintained that the eggs used in the 2004 cloning research were obtained ethically from 16 volunteers who had not been paid for the 242 eggs they had donated.

He has also strenuously denied allegations which first surfaced in the journal Nature last year that some of the eggs used in this study came from junior members of his own team.

On Tuesday, however, the Korean television station MBC claimed to have obtained documents allegedly showing that hundreds of human eggs may have been purchased for use in the cloning research.

The station also interviewed a woman who said she was one of Hwang's assistants, although she said she would not comment in detail about what happened until Professor Hwang makes an official statement following an internal laboratory investigation.

Professor Hwang meanwhile told the television station that junior scientists in his team had consulted with him about donating their own eggs but that he had persuaded them not to do so.

However, he also admitted that he had failed to check whether they had in fact gone ahead with donating their own eggs.

The dispute between the two scientists appears to centre around statements by Roh Sung-il, chairman of the board at Mizmedi Hospital in Seoul, who said that he paid the equivalent of about £1,000 (NZ$2485) each to about 20 women who had donated eggs for use in the research.

Mr Sung-il said that he paid for the eggs because there were not enough voluntary donors, although he also added that Professor Hwang was unaware of the transactions.

Donald Kennedy, the editor-in-chief of Science, said that he is taking the allegations very seriously and that he will take "appropriate action" if the allegations are substantiated.

Professor Hwang has refused to comment on the allegations but has told Science that he is investigating the matter further and will announce his conclusions as soon as possible.

Other stem-cell researchers are meanwhile bracing themselves for a backlash given that opponents to the research will use the dispute as evidence that scientists cannot be trusted.

Hans Schoeler of the Max Planck Institute for Molecular Medicine in Germany, who has visited Hwang's lab, said that the entire field of stem cell research could be affected, especially in countries such as his where the research is already unpopular.

"One argument will be that if Hwang was dishonest with a collaborator, how dishonest will he be toward the public," Dr Schoeler said.