"I was totally taken aback; no doubt about it," he told the Independent on Sunday last week. "I was absolutely confident I wouldn't find anything. But the longer I spent on the experiments, the more uneasy I became."
His unexpected findings have landed him, bewildered, in one of the hottest scientific controversies for years. They have abruptly ended his career, and destroyed his international reputation. He was magisterially rebuked by a score of Britain's most august Fellows of the Royal Society, attacked by a collaborator on the study, and accused by Sir Robert May, the Government's respected Chief Scientific Adviser, of violating "every canon of scientific rectitude". Only now is he able to reply.
I spent nearly six hours with him in his modest semi-detached home in Aberdeen on Wednesday, as he told his side of the story in full for the first time. He is a small, vital man - grey-faced with the strain (he has recently had a minor heart attack which he ascribes to it), but retaining a self-deprecating humour - he spoke of the "intolerable burden" of being unable to clear his name.
From the day after he briefly mentioned some of his findings on television in August until three weeks ago, he was bound to confidentiality by his employer for 37 years, Aberdeen's Rowett Research Institute. Since then he has been preparing to make his case before the House of Commons Select Committee on Science and Technology tomorrow.
"All I need is a chance," he said. "For the past seven months I haven't had one. I could not even defend myself against very heinous accusations. Sometimes I felt I should just get on a plane and go away. I couldn't take it."
It has been a devastating end to a brilliant career. He is the son of a Hungarian wartime resistance hero and fled when the 1956 rising was suppressed. But he had published his first scientific papers while still at university, and the Ford Foundation found him in an Austrian refugee camp. They gave him a scholarship to study anywhere in the world he chose.
He picked Britain, partly "because I knew I was an odd sort of guy, and the country then had a certain tolerance". He was recruited to the Institute in 1963 personally by Dr Richard Synge, a Nobel prizewinner in chemistry.
Dr Pusztai, 68, has published 270 scientific papers, and the Institute acknowledges he became "probably the world's expert" on lectins, proteins used in genetic modification. So valuable was his work he was asked to stay on after retirement age.
His nemesis began in 1995, when his group beat 27 contenders to win a pounds 1.6m Scottish Office contract to test the effects of GM foods. He was particularly interested because he could find only one previous peer-reviewed study on feeding them to animals. It was led by a scientist from Monsanto, the controversial GM company, and found no ill-effects.
Dr Pusztai fed rats on two strains of potatoes genetically engineered with a lectin from snowdrop bulbs, a third with the snowdrop lectin simply added and a fourth of ordinary potatoes.
He has been repeatedly accused by top politicians and scientists of merely adding a poison to potatoes. But he says he spent six years up to 1990 proving the snowdrop lectin was safe, even at high concentrations - and it is due to his work that it is used in genetic engineering at all.
To his surprise he found the immune systems and brains, livers, kidneys and other vital organs of the rats fed the GM potatoes were damaged, but not those of the rats fed the ordinary ones or those simply spiked with the lectin. This, he says, suggests the genetic modification could be largely to blame.
By last summer, he says, the Scottish Office money was running out, and the Institute refused funding. He therefore agreed to appear in a World in Action documentary, with the Institute's support, to raise the profile of the work in the hope of attracting funds. He says the Institute's press officer sat through the interview and no objection had been raised to what he had said in the seven weeks before screening on 10 August last year.
He was "absolutely surprised" his brief comments hit the headlines, but the Institute put out press releases supporting him the same day, and the next. But on 12 August he was suspended from work on the experiments. The study was stopped.
He worked out his contract until the end of the year, but found himself "sent to Coventry" by his colleagues. His computers were "sealed" and all his data from the experiments "confiscated". Dr Pusztai was forced into retirement.
An audit committee of four scientists, set up by the Institute, reviewed his work and disagreed with his conclusions. He says he was given three days to write a reply, without access to his full data.
This reply, which the Institute put on the internet, has been attacked as "unpublishable". He agrees and says this is hardly surprising given the limitations. He has also been condemned for not publishing a refereed scientific paper in the normal way. He says this was impossible without access to the complete data, which he has only just recovered.
Martin Polden, of the law firm Ross and Craig and president of the Environmental Law Foundation, who has taken up Dr Pusztai's case, says this is "a classic case for the need for open-ness in science". The Institute says it has nothing to add to previous statements.
Dr Pusztai insists: "I believe in the technology. But it is too new for us to be absolutely sure that what we are doing is right. But I can say from my experience if anyone dares to say anything even slightly contra- indicative, they are vilified and totally destroyed."
But surely others will do the same research elsewhere? "It would have to be a very strong person. If I, with my international reputation, can be destroyed, who will stand up?"Reuse content