He also found around 50 per cent of the credits â€“ worth $200 million â€“ issued in NSW and Queensland for forest regrowth were for projects where the forest cover actually declined.
The Clean Energy Regulator rejected Professor Macintoshâ€™s claims. It said in a statement that the fund has a â€œhigh degree of assessment and we do not believe this assertion to be trueâ€, but it will analyse his studies.
The land sector is crucial to Australiaâ€™s pledge to reach net zero by 2050. It has delivered 20 per cent of the emissions reduction to date, and the federal government is banking on farmers delivering 20 per cent more by 2050.
Farmer Mark Wootton owns significant livestock on his 3500-hectare property in western Victoria, with 2000 Merino sheep for wool and 500 head of beef cattle.
He has established a carbon-neutral brand, Jigsaw Farms, to market premium meat and wool by offsetting livestock carbon emissions with 600 hectares of revegetation, which is split between plantation timber and native forest habitat.
He said Professor Macintosh had raised valid criticisms about the standards that could undermine the commercial value of any farmer relying on their carbon-neutral status.
â€œMud sticks and thatâ€™s what thatâ€™s what I find really frustrating because thereâ€™s some good people doing really good work,â€ Mr Wootton said. â€œWe need those offsets to have integrity or else it damages our reputation when we go to sell our products.â€
Energy and Emissions Reduction Minister Angus Taylor said he rejected any assertion the fund was a fraud, arguing Australian carbon credits are valued as much as 10 times higher than comparable schemes.
â€œThis is a market which is considered to be one of the highest integrity markets in the world. And that shows up in pricing,â€ Mr Taylor said.
General manager of agriculture think tank the Australian Farm Institute, Katie McRobert, said questions over the integrity of carbon credits would deter investment in carbon farming, which not only reduces greenhouse gases but can help boost the sustainability of agriculture.
â€œThis will put a handbrake on the market and that would inadvertently put a handbrake on carbon sequestration activities. Thatâ€™s a problem because thereâ€™s no reason for Australian farmers and primary producers to stop doing carbon abatement activities,â€ she said.