The assessment from Bob Brown, former Greens leader and luminary of Australian environmentalism, is bleak and to the point: “There is a serious effort to bulldoze the environment movement and bury it.”

In the past couple of years, climate change infrastructure has been demolished, emissions trading put on ice. Scientists have been defunded and their ministry axed. Environmental Defenders Offices have also been defunded, the renewable energy sector thrown into chaos, the renewable energy target slashed and the astonishing notion mooted that we should burn trees to meet it.

The most recent move in this war on the environment is a parliamentary inquiry into the eligibility of environment groups to receive tax-deductible donations. It sounds like a minor issue but it could mean many of Australia’s most prominent and successful environment groups crumble.

“The mining lobby does not like rigorous, independent community scrutiny…”

Like Brown, veteran campaigner Cam Walker believes the government is bent on dismantling the green movement: “We’re under the hammer and, in my long time at Friends of the Earth, I’ve never seen anything like it. We haven’t seen the end of their agenda yet but we’re getting to the pointy end. And, yes, there is an attack on the green movement and it’s ideologically driven.”

Bob Brown says the current anti-green political climate is part of a long-term project “by movers and shakers in the corporate world, who have taken their cue from the United States [and Canada], where efforts to use the law to dampen down environmentalism are well advanced.

“Loggers and miners and exploiters have much greater access to ministerial suites in Canberra than do environmentalists – much greater – and they use that access to put forward legislation. They’re doing that now at a state and federal level to great effect.”

Jeff Angel, executive director of the Total Environment Centre, believes the anti-green push is being driven by a combination of a far-right culture war in parliament and a mining industry in a hurry to dig up and sell off as many fossil fuels as possible.

“The mining industry has always attacked the environment movement,” he explains, “but, in the last few years – with the carbon price, with the divestment push, with some wins in courts and planning inquiries, and with the very prominent campaign, during the last Queensland election, to save the [Great Barrier] Reef – the industry has been starting to feel the heat, so they’ve become more vicious.

“The mining lobby does not like rigorous, independent community scrutiny that can translate into policies and laws that might curtail their ambitions. And I think they are so fanatical that any defeat has to be stomped on and exterminated. That fanaticism feeds their anti-democratic push to undermine planning laws, override public inquiry results and attack the funding of environment groups.”

These attacks are not reserved for the big players. Relatively small community groups have also alleged that they’ve been victims of intimidation, misinformation and even espionage.

Helen War, a campaigner with Front Line Action on Coal, spent much of 2014 at a protest camp just outside the tiny northern New South Wales village of Maules Creek, where Whitehaven Coal was rapidly expanding its mine into the Leard State Forest. She remembers weeks when roadblocks were installed unnecessarily, impeding the travel of locals. Cars were pulled over and searched. Surveillance planes buzzed the farmhouses of dissenters. There were times when it felt like a war zone.

“Their main tactic was intimidation,” she explains. “As time progressed, the security officers wore increasingly militarised uniforms and balaclavas. They also used physical violence. A young photographer was assaulted by a security guard and held down against her will. People were pushed to the ground and pushed off roads. Completely non-violent, passive acts were met with undue force. Then finally spies were sent in to infiltrate the community camp. A lot of it was simply to scare people.”

John Hepburn, executive director of the Sunrise Project, which offers small grants and training to community groups fighting local environmental battles, believes mining companies have overreacted to community objections because they have misunderstood the motives behind them.

“At the height of the coal boom, in 2011, there were over 100 new coal projects and coalmine expansions all over the country. As a result of that, farming communities and regional communities, from one end of the country to the other, arced up and said no,” he says.

“I think the industry has completely misunderstood it. The industry thinks that this movement has been somehow constructed by the big green groups, but that’s not the case. This is a genuine grassroots backlash… It’s not a response that anyone can control – not the environment movement, not industry, not government – because it’s a genuine community response to a mining industry that is out of control.”

But whatever the suite of influences behind the latest threat to the green movement – the inquiry into the Register of Environmental Organisations – there is general agreement it has teeth.

Greenpeace CEO David Ritter cautions those who would dismiss the inquiry lightly: “Some people have looked at this and said, ‘Yes, it’s an inquiry but it will never get through the senate, so why are you worried?’ Well, I think this one could actually land.”

As Friends of the Earth co-ordinator Cam Walker explains: “The government says, ‘Oh no, we’re not attacking freedom of speech because we’re not preventing you from speaking. All we’re saying is that you can’t receive a tax benefit for your activities.’ But they know that the vast majority of the income for green groups is reliant on tax-deductible donations – particularly now the government has killed off all the federal funding that has traditionally kept the green movement afloat.”

Walker points to the Grants to Voluntary Environment, Sustainability and Heritage Organisations program, which has been maintained by both Liberal and Labor administrations since the early 1970s, only to be axed in 2014 by the Abbott government. “It’s clear what’s going on,” he says. “They’ve pushed us back onto tax-deductible donations to survive and now they’re taking away those last remnants of our livelihood.”

Queensland senator Matthew Canavan says that of the 600 green groups on the register he has 100 or more in his sights for ditching – some because they’re too politically active, others because members have broken the law. He, like the Minerals Council of Australia, is particularly suspicious of abseilers and proposes groups be disqualified for eschewing hands-on conservation activities and engaging in “political debate”.

The inquiry’s convener, Liberal MP Alex Hawke, cautions groups against premature panic but concedes that the inquiry will look at “the activities undertaken by organisations currently listed on the register and the extent to which these activities involve on-ground environmental works.”

He insists that “the inquiry’s purpose is not to restrict environmental activity but to examine under what conditions an organisation on the environment register should receive taxpayer funding.”

Peter Seidel, adjunct professor of law at La Trobe University and partner in public interest law at Arnold Bloch Leibler, represents a number of the groups that could be affected. He

believes it is “very likely the Coalition members of the committee will recommend instituting a similar model in Australia to the existing, overly prescriptive and artificial model in Canada”. There, only 10 per cent of a charitable organisation’s funds can be spent on political activity, and involvement in politics must remain “ancillary or incidental”.

Seidel says there would be no need for parliamentary approval to institute Canadian-style changes to eligibility for the register: “Not if they’re included in new ministerial guidelines or rules.” But he warns that any changes to those rules and guidelines that “compromise the ability of environmental organisations to engage in political advocacy” will lead to a High Court challenge.

Seidel believes there’s a fair chance that any such challenge would be successful. He points to the precedent set in 2010 by Aid/Watch Incorporated v Commissioner of Taxation. The High Court held that Aid/Watch was not disqualified from operating as a charity, even though its activities involved agitating for legislative and political change. According to the court: “Political speech by charities enriches the political process by encouraging political debate, facilitating citizen participation and engagement and promoting political pluralism”.

But before then, the green movement might have spent a year – plausibly longer – starved of funds. “One could argue,” says Walker, “that it’s part of their plan, because the time I’m spending working on this would be better spent supporting community groups and defending the natural environment. So, in some ways, they’ve already succeeded, because they’re diverting scarce resources away from protecting the environment into defending ourselves.”

David Ritter is not so sure. “They want to distract us from our core business but this inquiry has had the opposite effect. The industry has tugged at some Coalition MPs, who have done exactly what the industry wanted, which was to place a greater tax burden on the hundreds and thousands of – let’s use their language – mums and dads and families around Australia who give their 20 or 30 bucks to environmental organisations to protect the Great Barrier Reef and clean water and clear skies. So, yes, there are dangers in it for organisations like Greenpeace but it is a front-and-centre opportunity to have the conversation we need to have about the over-mighty power of this arrogant industry that wants to sell out the country’s future. I’m sure they thought this was just going to tie us up in knots, but that hasn’t been the outcome.”

These latest volleys do not faze elders such as Bob Brown. This is a movement forged of resistance. “One of the reasons I established the Bob Brown Foundation was to stand against this tide,” Brown insists. “We’re going to do our job and we’re not going to be dumbed down by threats.”