Australia's deadly red-back spider has established itself in New Zealand, posing a significant risk to humans as it threatens to colonise major cities, researchers have found.

The venomous red-back, a relative of the black widow, is thought to have hitched a ride to New Zealand on imported goods from Australia.

It has established itself at sites on both the North and South islands, scientists said.

The government's AgResearch institute said in a study published this month that the red-back had proved more resilient to New Zealand's cold, wet winters than initially expected.

AgResearch scientist Cor Vink said the spider, named for its distinctive red stripe, threatened endangered native spider and insect populations.

"Having red-backs in New Zealand is also significant to public health because they have the potential to become established in a number of areas that are close to urban populations," he said.

Red-backs are common in Australian cities and Mr Vink said climate modelling showed they had the ability to thrive in New Zealand's urban areas.

The Australian Venom Research Unit says at least 14 people have died from red-back bites, although there have been no fatalities since an anti-venom was developed in the 1950s.

- AFP