A New Zealand researcher claims there is an over-representation of the "warrior" gene, which has been linked to aggressive behaviour, in Maori men.

Dr Rod Lea said the monoamine oxidase gene, carried by a large number of Maori, could be key to addressing health issues.

The genetic epidemiologist at the Institute of Environmental Science and Research in Wellington said the gene has been linked to aggressive behaviour as well as addictions to things such as tobacco.

Maori leaders said there were many other factors which dictated whether people turned violent, such as poverty.

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The gene was discovered by American researchers but had not previously been linked to an ethnic group.

Dr Lea, who has been speaking at an international conference in Brisbane, denies Australian reports that quoted him suggesting the gene has links to criminality.

Australian Associated Press quoted him as saying: "It is controversial because it has implications suggesting links with criminality among Maori people.

I think there is a link, it definitely predisposes people to be more likely to be criminals and engage in that type of behaviour as they grow older.

"There are lots of lifestyle, upbringing-related exposures that could be relevant here so, obviously, the gene won't automatically make you a criminal."

He said Maori were also more prone to obesity than white New Zealanders, and while the researchers don't yet know the role of lifestyle factors, they believe ancestral genetics played a vital role.

Small influence

Dr Lea said today he believed the influence of the gene, which appeared to feature in about 60 per cent of Maori men compared with 30 per cent of European men, could be small.

"I believe this gene has an influence on behaviour of humans in general, but I also believe that the influence is rather small," he said on National Radio.

"We have to be clear that behavioural traits such as susceptibility to addiction, aggressive behaviour, risk taking, all those sort of things are extremely complex and they are due to numerous factors including non-genetic environmental factors like upbringing and other lifestyle factors.