“All of us involved in public comment on both sides of the argument for and against GM - or any issue - need to be mindful about what we say about others,” he said.

“Any of us if we are unhappy about what has been said about us by someone else have a right to test the appropriateness of what was said in the courts.”

Dr Carman also confirmed she was taking legal action against several people for defamation but declined to make any further comment.

The WA Pastoralists and Graziers Association (PGA) confirmed receiving correspondence in September this year from a Melbourne-based law firm purporting to represent the SFF, but declined to provide any further comment.

Mr Crabtree said one of the defamation claims focused on “inferences and innuendos” contained in letters to the editor distributed to various media outlets earlier this year.

It’s understood the PGA claim is related to a media statement made in May this year relating to a consent order agreed to in the Kojonup case, prohibiting GM canola being planted on the Baxter’s farm within 1.1 kilometres of Mr Marsh’s organic farm.

Another leading biotechnology expert, who asked not to be named, said their university employer was “nervous” about the litigation threats and had urged more caution when making public comment on GM crops.

Mr Crabtree said he felt financially threatened by the potential legal costs of defending himself against the defamation claims, even though he felt he’d done nothing wrong.

He said he’d been advocating the benefits of biotechnology to Australian farmers for more than a decade, as an individual expert, farmer and agronomist based in WA, and did not act on behalf of a member group.

Mr Crabtree said he wanted to see farming groups take more of a leading role in GM advocacy, including WAFarmers and the National Farmers Federation (NFF).

He said he’d been fighting the GM issue since 2002 and in that time had written many letters to the editor, and been quoted in as many media articles or interviews, in trying to hold various GM cropping critics to account.

They include former WAFarmers grains council vice president and Network of Concerned Farmers national spokesperson Julie Newman, former Labor Agriculture Minister Kim Chance and Gene Ethics director Bob Phelps.

“I’d like to see our farm groups and leaders doing more work advocating GM crops and explaining to opponents… why farmers need the freedom to access this technology,” he said.

“Maybe they could start pushing for research that will give farmers access to a frost tolerant GM wheat variety one day or a GM variety with a broad spectrum of herbicide tolerance.

“If we had those two varieties in the tool kit it would almost certainly give grain farmers a quantum leap in production and productivity.

“And it couldn’t come soon enough, with farming margins under extreme pressure due to pressures from the mining industry, high input costs and the high Australian dollar.”

Grains Producers Australia R&D spokesman Andrew Weidemann said his group supported increased research into cropping biotechnology to explore its potential benefits to farmers, industry and consumers.

He said the world population was forecast to reach 9.2 billion by 2050 and GM crops had the capacity to alleviate global food production issues.

“We need as many tools as we can to ensure there’s enough food to feed the world’s growing population in future,” he said.

“We need to explore all of the options.

Speaking to Fairfax Agricultural Media in September, Dr Carman said she had many degrees and expertise in many areas including risk assessment and “simply reviewed the safety testing of GM crops and found serious deficiencies”.

“Going public with those concerns and providing a description of the safety testing that should be done is not anti-GM campaigning - my interest lies only in the proper scientific evaluation of the safety of GM crops,” she said.

Mr Kinnear has also expressed ongoing concerns about the safety of GM crops, including those raised in recent work published by French Professor Giles-Eric Seralini which suggested a link between GM corn and glyphosate and an increased incidence of tumours in rats.

However, the European Food Safety Authority issued a statement last month saying Prof Seralini’s paper failed to meet acceptable scientific standards.