The Korean scientists explain exclusively to the BBC why they performed their claimed experiment

The Korean Medical Association has produced a 10-page report which suggests that the cloning may not have been properly carried out. It even suggests that it may not have been done at all.

"They insist they did this, but I don't know," said Seo Chung Sun in Science magazine. He is a biochemist at Seoul National University and headed the investigation.

This photograph is the only remaining evidence of the cloned cells

"We don't have any material to judge. That's a big problem," said Dr Seo. The four cells claimed to have developed from an egg implanted with adult DNA were not preserved.

The scientists who say they performed the experiment at the Kyung Hee Health Centre in Seoul, Dr Kim Seung Bo and Dr Lee Bo Yon, gave their first in-depth interview to BBC One's Panorama, broadcast on Monday. They said their experiment was for research purposes only but observers believe their aim is human cloning.

Dr Kim said: "I believe the cloning of a human cell can provide a step forward in the treatment of human fertility."

He explained why his experiment had been stopped after the cloned cell had divided to four cells: this was the stage at which cells would be implanted into a woman's womb and, for research reasons, he wanted to see if this stage could be achieved by cloning.

Dr Kim Seung Bo: Cloning "much sooner than you think"

Professor Lee Silver, at Princeton University, USA, rejected this explanation. He believes the enormous outrage that followed the Korean scientists' announcement "forced them to backtrack and claim that it was only done for research. That makes absolutely no sense. Fertility clinics have one goal in mind - to help people have babies."

Asked when he thought a cloned human baby would be born, Dr Kim told the BBC: "Much sooner than you think."

His colleague, Dr Lee said: " I didn't start the experiment out of playful curiosity. I think this technique will help infertile patients a great deal."

These latest developments have further fuelled the debate surrounding human reproductive cloning.

Peter Blackburn says he would consider cloning a child

Peter Blackburn and his wife Ildiko told Panorama they were considering cloning as a way around their fertility problems. The computer consultants from Cambridgeshire, England said that the fact the baby would be genetically identical to one of them was not the point - "It's a child".

Dr Donald Bruce, a scientist and director of the Church of Scotland's Society, Religion and Technology Project, told the BBC he was sceptical that cloning could happen at present.

"When you try to clone mammals in this way, all sorts of problems occur. The Farm Animal Welfare Council are calling for a moratorium on commercial animal cloning until animal welfare problems have been resolved," he said.

Dr Donald Bruce explains his opposition to human reproductive cloning

Dr Bruce and his wife are childless and have attempted to conceive via IVF. But he believes reproductive cloning is also ethically wrong: "It's not a question of having identical genetics, it's a question of control - no-one has been able to do this until now."