Conservationist Bob Brown is "quite proud" of having been arrested while protesting environmental causes, he has told an inquiry into the tax-free status of environmental groups.

Mr Brown, who is head of the Bob Brown Foundation which campaigns for environmental conservation, was the first to front the federal Standing Committee on the Environment hearings in Hobart.

Liberal, National and LNP members of the committee are concerned that environmental groups are eligible for tax deductions but are using their donors' funds to bankroll illegal activities and political campaigns.

When asked about his own arrests during environmental protests Mr Brown invoked Mahatma Gandhi and Nelson Mandela.

"I would also like to remind you that Mahatma Gandhi and Nelson Mandela were convicted of protest as well," he said.

"If you want to put me in some lesser category with them then I'm quite proud of the fact."

Mr Brown had initially refused to appear before the committee and opened his appearance by claiming the inquiry was a poorly disguised attack on conservationists.

"The inquiry is a Liberal Party vendetta against environment groups," he said.

"They want to crush environment groups."

Committee chairman, Liberal MP Alex Hawke, denied the accusation and wanted to know what "on the ground work" the Bob Brown Foundation carried out, asking whether it did work comparable to land care groups.

The former Australian Greens Leader told the hearing he respected the law, but unlawful protests had achieved important conservation outcomes.

"We all, in a democratic society, have a right to peaceful and dignified protest when we think the wrong thing is being done," he said.

"I am very proud of the fact that the Franklin River is running free as part of the economic and employment well being of Tasmania in 2015."

Mr Brown said his foundation did much more than advocacy including travel and research, and cited a front page newspaper story to defend the success of his lobbying work.

The inquiry will probe: Definition of environmental organisation under the Income Tax Assessment Act

Definition of environmental organisation under the Income Tax Assessment Act Requirements to be listed and maintained on environmental organisations register

Requirements to be listed and maintained on environmental organisations register Activities undertaken by listed organisations and extent of on-ground environmental works

Activities undertaken by listed organisations and extent of on-ground environmental works Reporting requirements to disclose donations and activities funded by donations

Reporting requirements to disclose donations and activities funded by donations Administration of the register

Administration of the register Measures available for tax office to investigate breaches

Measures available for tax office to investigate breaches How international jurisdictions administer governance

He also denied his organisation was closely involved in bankrolling political campaigns, but told the committee "everything is politics".

When asked whether his organisation participated in illegal activities Mr Brown said he had "enormous respect" for the law.

Environment Tasmania's spokesman for forests, Andrew Perry, was the inquiry's second witness.

Mr Perry was asked to explain why his organisation spends two-thirds of its budget on wages and administration and the rest on activities, like land restoration.

"We have many examples of good outcomes," he said.

"I'm very proud of the organisation's role in the apolitical forest peace deal a few years back.

"I'm also very proud of the restoration work that's happening on the skyline in the north-east which is employing a lot of local workers from the north-east.

"It is employing often displaced forestry workers."

The hearing also held a moment's silence to mark the death of the Australian Marine Conservation Society's Felicity Wishart, who gave evidence to the committee last week.