Battle lines have, according to this story, been drawn for a clash of two of the titans of the genetically modified ( GM ) crop debate in Edinburgh today when Dr Arpad Pusztai, the scientist sacked by the prestigious Rowett Research Institute in Aberdeen for whistle-blowing, and Professor Tony Trewavas of Edinburgh University debate head to head. Holding the jackets at the Royal Botanic Garden will be the McCarrison Society, a body which explores the links between nutrition and health.

The story says that since being 'silenced', Dr Pusztai has lectured by invitation worldwide. His itinerary has included Canada, Japan, India, Bulgaria, Colombia, and every EU country. He has just returned from giving evidence to New Zealand's government commission - at the commission's request - which will determine the future of GM in that country. Professor Trewavas, of the Institute of Cell and Molecular Biology at Edinburgh University, is a powerful international voice in favour of GM research whose primary concern is how agriculture is going to resolve the enormous complications being wrought by global warming and population growth.

Dr Pusztai describes the current state of GM research as 'target-shooting blindfolded' but acknowledges his work is at an end. The 20-strong team of scientists he headed at Aberdeen has been disbanded, he claims, with 18 of the 20 'drifting away' from the Rowett. 'They were treated like pariahs,' he says. 'Other scientists they had known for years were afraid to speak to them. I grew up first under the Nazis and then the communists so I was not surprised. I regard my role now as a communicator. These are issues people ought to know about. The research was funded by the taxpayer and my allegiance is to the taxpayer. This is the most secretive country in the world but these are issues the ordinary man in the street must know about. After all, he is eating the stuff.'

Hungarian-born Dr Pusztai, 44 years in Scotland and with a worldwide scientific reputation, made a 150-second appearance on World in Action in August 1998, in which he voiced concern that the testing procedures on food containing GM material might not be adequate. All hell broke loose : with hindsight, many in science believe what happened next came right from the heart of government in both London and Washington, where successive administrations are known to clasp the vast GM industry to their bosom.

Within a few days, he was suspended from the Rowett, allegedly for releasing misleading and incomplete information, and silenced by the threat of legal action. His sin was to disclose the findings of his recent research - that the growth and immune responsiveness of rats fed on a diet containing GM potatoes were depressed. The establishment closed ranks, and a secret and anonymous peer review group discredited his research. But, the story says, an international panel of scientists, using the same data from Dr Pusztai, rejected what they said was a selective and biased audit and vindicated Dr Pusztai's work and scientific concerns.

Dr Pusztai was quoted as saying, 'In a scientific argument we need facts but in this argument nothing has been published by the other side. Instead we have these high and mighty people telling the public they have looked at all the facts and they think everything is all right. It is a condescending attitude which says that 'you little people cannot understand this high science. We will make the judgment for you - just go and buy the stuff and eat it'. This is absolutely ludicrous. Why should we take their word for it?'

Dr Pusztai, now 70, adds that he first met Ralph Nader in America in 1967 when he was in the throes of exposing the criminal state of car safety. The motor industry and the US government tried to destroy Nader but he was right about car safety, was right subsequently about many other issues, and has now had more consumer legislation passed through the US Senate than anyone else. He is now taking up the issue of GM safety in the US and Canada. The parallels are obvious.

The story goes on to say that the ultimate reason the government and the scientific establishment did not want Dr Pusztai's work to be completed was that ordinary people would readily grasp what it was about, he believes. 'I have never had any problem explaining anything to people. Even complex molecular biology can be explained. The concepts are easily understood. The body is dependent on its immune system for protection in a very hostile world. If you are eating something which is interfering with the speed of your response that is not a good idea.'

Rat and human immune systems are distanced by several million years of evolution but, he says, they are basically the same. 'We do not know if the changes we found to the rats' immune systems were temporary or permanent or reversible. We could have found all this out and we had the plans in hand. Why did they stop us? The reason was, they were afraid.'

Professor Trewavas was quoted as saying, however: 'People are fussing about what is in their food at the moment but I think it is only a matter of time before they get used to the idea. They are fussing about it because of the lack of knowledge.' His view is that we require GM for the future of mankind, so he cannot understand why such a fuss is being made. Scientists have been shuffling genes from weeds to crops for some time and have been bombarding plants with X-rays and radiation to generate mutants, and many such crops are currently available and in extensive use.

Long experience, he says, has taught him a different perception of what to be concerned about and persuaded him that there is nothing wrong with GM .

Dr Pusztai, he claims, stands alone in the debate and he has become involved in personalities. 'I think that is unfortunate. I will tell him right at the outset that everything which has happened to him is his own doing. He has this idea that I had a hand in the science festival episode' - Dr Pusztai was first invited to speak at Edinburgh Science Festival but then told the invitation was withdrawn - 'which is not true. He has become paranoid about those he sees as enemies. But he has made his own bed and he must lie in it. 'He spoke to the media about unpublished research and he has got to accept responsibility for what he did. He has published more than 300 papers in the best scientific journals. He is an expert in lectins. He decided to blow it all in 150 seconds on television. I have no doubt that what has happened to him is a tragedy.'

Professor Trewavas was cited as criticizing Dr Pusztai's researches as having 'too many things missing' for anyone to make any deductions. He claims Dr Pusztai is selective in not describing other scientists' papers which relate to very detailed investigations but which have found nothing.

'I think it is time he stopped saying that not enough has been done. A vast amount of science into the possible effects of GM has been done,' he states. The Food Standards Agency is, he claims, 'perfectly happy with what is on offer at the present time', and goes on to criticise environmentalists who respond in terms of a political agenda which ignores the science. The idea that once genetically altered material is released into the wild it can never be recalled is a case in point. No crop has the ability to survive in the wild, he maintains, because they cannot behave as wild plants - weeds - do. Crops, including genetically modified crops, die out after two or three years and vanish.

Of his recent all-out attack on organic farming published in Nature and then repeated in the Daily Telegraph, Professor Trewavas was quoted as saying, 'I want to start a debate about organic farming because there is none at present and that is wrong. The so-called benefits are largely based on assertion. We need to be aware of what we actually want, The human race has always tried to keep progressing while minimising damage - the aeroplane and the car are perfect examples. Who now would chuck them away?' Criticism by scientists of GM may have been muted, perhaps by self-censorship or otherwise, after Dr Pusztai's high-profile sacking. The issues will, however, return to centre-stage today.