THE chair of the Abbott government's climate change advice agency, Bernie Fraser, has resigned without explanation.
It comes less than a month after Mr Fraser issued a strong rebuke to Abbott government over its justifications of its post-2020 greenhouse emissions targets.
A statement issued by the Climate Change Authority late on Tuesday said Mr Fraser, a respected former Reserve Bank governor, had quit as chair.
"The authority members thank Mr Fraser for his enormously valuable contribution to the authority's work in providing independent expert advice to the Australian government and Parliament on climate change," it said.
"Arrangements have been made to ensure the authority's work will continue uninterrupted."
No further explanation was provided. It is understood Mr Fraser had a difficult relationship with Environment Minister Greg Hunt.
Fairfax Media understands Mr Fraser announced his decision on Tuesday after an all-day meeting of the authority.
Many of his colleagues are believed to be deeply saddened by his departure. He is not believed to have quit due to personal problems such as a health issue.
A spokeswoman for the authority said Mr Fraser did not wish to comment on his resignation.
The government sought to abolish the authority last year but was blocked in the Senate. The agency was set up by the former Labor government to provide independent climate change advice.
Mr Fraser's departure means five of the nine board positions are vacant. The authority's management will be led in the interim by Professor David Karoly, a climate expert at Melbourne University.
In September last year Mr Fraser said morale at his agency had been hit hard by the government's attempt to cull it.
"It's understandably having a pretty devastating effect," he said.
He said even with some staff departures, the authority retained a "core capacity" to help the government develop a policy to restore bipartisan support for renewable energy.
But Mr Fraser said despite this "we have not been invited" to assist the government on the issue.
In a statement late on Tuesday, Mr Hunt thanked Mr Fraser for his work.
"He has had an outstanding career in public service, which I deeply respect and acknowledge," he said.
"In particular, I thank Mr Fraser for his assistance with the crossbench in the passage of the Emissions Reduction Fund."
He said the vacant positions "will be filled in the near future".
The authority had urged the government to impose extra scrutiny on polluters to ensure that, under the Emissions Reduction Fund, billions of taxpayer dollars are not spent on emissions cuts that would have occurred anyway. The government rejected the call.
Mr Fraser was an outspoken advocate of climate change action. In a strongly worded statement last month he directly contradicted government claims about emissions targets it would take to global climate talks in Paris later this year.
In the statement, Mr Fraser said Prime Minister Tony Abbott's assertion that its emissions cuts were akin to the United States were incorrect, and in fact Australia's targets put the nation "at or near the bottom" of comparable countries.
He said on the basis of the government's current targets, Australia "would slip further behind the efforts being made by comparable countries and likely face large catch-up adjustments down the track".
Mr Fraser said Labor's proposed emissions trading scheme does not equate to a new carbon tax, contrary to the government's characterisation.
The government intends to reduce the amount of greenhouse gas released into the atmosphere by 26-28 per cent by 2030, based on 2005 levels.
In April this year the authority was critical of the government for "skipping over" the significance of climate change for future generations in its recent Intergenerational Report, which sets out government budget challenges over the next 40 years.
With Lisa Cox, Peter Hannam