His research was described by Time magazine in a cover story as meaning "something awful for just about everyone". All over the English-speaking world and beyond, variants of the headline "Mommy Wars" appeared. It was a strong response to a short and turgidly-written psychological research paper, but it wasn't surprising, because Prof Jay Belsky was saying something shocking: if children spend more than 20 hours in childcare from an early age and more or less continuously through their first five years, they are likely to be more aggressive and less well-behaved.

In fact, Prof Belsky was revisiting old ground. He first presented this thesis in 1986 to a storm of controversy. Not daunted, he continued his research and earlier this year presented it much less tentatively in "Developmental Risk (Still) Associated with Early Child Care". This time he had more evidence. The National Institute of Child Health and Human Development Study of Early Child Care studied over 1,000 children from 10 US communities. It found that children who had spent a lot of their early years being cared for away from their mothers had higher levels of "problem behaviour" by the time they reached school.

It's all a right-wing plot to put us all back in the kitchen, right? When it comes to this issue, women tend to act like the citizens damaged by a terrible dictatorship, always on the look-out for a conspiracy theory. And it isn't surprising. But Prof Belsky, American, but now director of the new Institute for the Study of Children, Families and Social Issues at Birkbeck College, London, claims he is just a scientist trying to establish the truth. "Don't shoot the messenger," he pleads.

I had read those lines in other interviews with Prof Belsky. It seems he has not been unscathed by the backlash against his research, and is a bit of a conspiracy theorist himself.

When I talked to him he slipped so quickly into self-defence that it was actually difficult to tease out the issues. At the same time, parrying with the media seems to have a dangerous fascination for him. I asked him did he have moral reasons for promoting his research?

"Not really," he said. "I've been studying this problem for over 30 years and while, sure I'm interested in its social implications, I am a scientist and what I am mainly interested in is: what is the evidence? But between evidence and implications there's something called values. For example, there's evidence that smoking can kill but that doesn't mean we should prohibit tobacco."

It seems a preposterous analogy. The increase in the level of aggression and non-compliance which a high dosage of childcare seems to produce is small. What bothers him, he says, is that when there is a small finding which tells us what we want to hear - like that high-quality childcare has positive implications for cognitive and language development - it is deemed important; but when it's news we don't want to hear it is poo-poohed.

In fact, the earthquake which followed the publication of Belsky's research last year was followed by a tidal wave: the voices of 12 other academics involved in the Early Child Care report saying they didn't agree with the way he interpreted the statistics. The leading statistician on the project was quoted in the Guardian as saying: "Our results do not actually support his conclusions."

At the time, Belsky was not commenting on the issue but today he is. He calls these critics "ideologues masquerading as scientists. They're making fools of themselves and a mockery of social science".

Even if the increase in aggression in childcare-raised children is small, he says, if it is replicated in a large number of people, there is a "social algebra" which magnifies its effects.

"It will matter if you're a teacher and you've got 25 eight or nine-year-olds and half of them have spent lots of time in childcare and sometimes low-quality childcare; they will be more aggressive and less intellectually capable."

Surely the rights of the individual child should be more persuasive than the effects of children's behaviour on the rest of us? He agrees and says he would justify "on humanitarian grounds alone" extended parental leave, preferably paid, and part-time work for mothers which would "reroute back to their pre-pregnancy jobs".

He also believes in high-quality childcare but he wants to reduce the dosage. "It's not all or nothing. The issue is not to eat or to starve. It's a question of cutting down your consumption. That's the way the childcare discussion should go."

Studies have shown, he says, that parents want to stay home with young children, and even in Sweden, where there is high quality childcare, parents take advantage of long leave to look after their children themselves.

He doesn't aim to direct mothers back to the home, however, and says that if long hours spent in daycare mean an emotional "cost" for a family "maybe that cost is compensated for by some other gain".

Newspaper articles question his motivation, but the fact that at the beginning of his professional life he co-authored a paper which asserted that the risks for children attributed to childcare could not be substantiated is strong evidence that he went into this research with his eyes open.

When I ask how he became interested in the subject he tells a story about the day he was sitting under a tree when a friend came by with "a bunch of little kids in tow" from the childcare facility at the university hospital. "The rest is history", he says - he moved university and enrolled as a psychology student to study child development and work in a childcare setting.

Prof Jay Belsky will address a seminar, "The Early Years", organised by Women in the Home at Buswell's Hotel, Dublin, today from 2pm-5pm. The other speakers are the Governor of Mountjoy, John Lonergan, and Irish Times columnist Breda O'Brien