THE environmental and animal-welfare movement's war on agriculture has has seen death threats against scientists.

The revelation follows last week's sabotage of CSIRO's genetically-modified wheat trial near Canberra by Greenpeace.

It has left agriculture scientists afraid to work alone or late at night for fear they will be attacked.

Co-operative Research Centre Association chief Tony Peacock said the violent threats were increasing.

"Breaking, entering and destroying CSIRO's work can't be regarded as non-violent protest," Dr Peacock said.

"It makes people fearful of working early, late or alone.

"It is straight-out intimidation."

Dr Peacock, who represents the nation's top 44 co-operative research bodies, said the Greenpeace attack followed many recent threats to Australian scientists and their work.

"Colleagues of mine have been receiving 'wishes' from animal welfarists that they die a long and painful death - presumably because we are involved in restoring some native animals to a sanctuary which involves culling other animals," Dr Peacock said.

The threats were made against ecologists on Canberra's Mulligan's Flat Woodland Sanctuary Board of Management, after they culled the sanctuary's kangaroo population.

"Climate-change scientists at the ANU (Australian National University) have had to be given a higher level of security following email threats that are apparently extraordinarily vicious," Dr Peacock said.

He said Australian researchers have long been privileged to conduct their work free from fear, but they were being forced to adjust their attitudes after recent events.

Dr Peacock also said the cost of research would climb because of the threats.

"It has immediately increased the cost of doing trials because CSIRO and other research institutes will now have to increase security," he said.

Greenpeace has justified its activists' actions by issuing a media statement stating the GM wheat should never have left the lab.

Greenpeace activist Heather McCabe, who has admitted being involved in whipper-snippering the GM wheat, said she was "sick of being treated like a dumb mum who doesn't understand the science".

"As far as I'm concerned, my family's health is just too important," she said.

"GM wheat is not safe, and if the government can't protect the safety of my family, then I will."

But Dr Peacock said Greenpeace's justification that 'if the government can't...I will' didn't wash.

"It's the same line of reasoning a fringe anti-carbon tax protester used ... to justify taking up arms," he said. "It deserves the same level of condemnation."

Since 2005, CSIRO, the University of Adelaide and the Victorian Department of Primary Industries have conducted 11 small GM wheat field trials, 10 of which are still current, on traits such as altered starch content, salt and drought tolerance.

CSIRO has refused to comment on the Greenpeace attack, with a spokesman saying the matter had been referred to the police.

"Until that investigation is complete we won't be saying much," the CSIRO spokesman said.

The attack occurred some time last Thursday night and involved at least three Greenpeace activists wearing hazmat suits, two of whom used whipper-snippers to destroy the 0.5ha of fully netted plots.

The plots were netted to reduce the risk of contamination of conventional wheat.