Planned changes to Australia's carbon credit scheme will punish good projects and could increase greenhouse gas emissions, a whistleblower warns.
Professor Andrew Macintosh has also hit back at criticism by Climate Change Minister Chris Bowen, who he accuses of trying to discredit his work on the integrity of the carbon market.
Working with other Australian National University and University of NSW researchers, Prof Macintosh warned almost a year ago that the scheme was a "fraud on taxpayers and the environment".
Their analysis found up to 80 per cent of credits issued under three of the $4.5 billion federal Emission Reduction Fund's most-used methods for generating carbon credits were questionable.
The claims were dismissed by the regulator administering the fund and the Emissions Reduction Assurance Committee - chaired by Prof Macintosh for six years under the coalition government - which assesses the compliance and integrity of abatement methods.
But the furore helped spark an independent review, the recommendations of which were adopted this week by the Albanese government
The review led by former chief scientist Ian Chubb found the system, used by companies to offset greenhouse gas emissions, was well designed.
It also rejected criticism that the level of abatement achieved under the scheme was overstated but agreed the process needed to be conducted with more public scrutiny instead of behind closed doors.
Defending the review and government's response, Mr Bowen said he understood Prof Macintosh had "a different view".
"He has in the past defended some of the methods that he's now criticising," the minister told ABC Radio on Wednesday.
But Prof Macintosh said Mr Bowen had caused hurt and disappointment with his remarks, adding he had written to the minister.
In his letter, he said Mr Bowen's comments followed the same line former energy minister Angus Taylor used to discredit the researchers' work.
"The decision to go public has come at a great personal and professional cost, for all of us and our families," he wrote.
Prof Macintosh added he appreciated the need for pragmatism in the development of climate policy, but he believed it was important financial markets like the Australian Carbon Credit Unit market were regulated and administered in an open and robust manner.
"Modern history is littered with examples of financial market collapses that have been caused by regulatory failures that are traceable to closed regulatory cultures," he wrote.
Prof Macintosh told AAP he was concerned changes to the scheme would punish good projects by imposing a burden across the board and making quality projects less likely to be financially viable.
An immediate change to the scheme is the scrapping of the contentious "avoided deforestation" method that generates carbon credits for protecting native forest from land clearing.
But revoking the method does not affect existing projects, leaving taxpayers on the hook.
Prof Macintosh said "high-risk" credits from these projects could be sold into the carbon market and used by heavy industry to authorise emissions above limits set under the Safeguard Mechanism, resulting in an overall increase in emissions.
"It's going to affect the integrity of the Safeguard Mechanism," he said.
Carbon credits are a centrepiece of Australia's climate policy along with the mechanism that sets a limit on emissions by heavy industry.