Big carbon producers will be able to pay only a tiny fraction of their profits to continue polluting, raising concerns about Australia's ability to reduce emissions.
New analysis shows energy companies will sacrifice only a small share of their incomes to buy carbon credits to offset emissions which go above a government-set cap.
The Greens say the figures show major fossil fuel producers will be able to afford to keep polluting under the existing safeguard mechanism.
"These big corporations that are bringing in billions of dollars a year in revenue won't actually be forced to cut their pollution," leader Adam Bandt told ABC radio.
"Instead they'll just be able to pay to offset it."
Based on figures from the Parliamentary Library, Woodside Energy would need to pay less than $3 million to offset its pollution, he said.
The company posted a half-yearly after-tax profit of nearly $2.4 billion earlier this year.
The Greens also calculated coal mine operator Anglo-American would only need to pay 0.2 per cent of one year's profit to cover five years' worth of abatement.
Mr Bandt said the costs were "coins down the back of the couch" for the companies.
"The proposed design of the scheme from what we've seen from the discussion paper so far suggests many of these big corporations won't have to cut their pollution at all," he said.
Mr Bandt said the Greens would use their numbers in the Senate, where the party holds the balance of power, to strengthen the safeguard mechanism and push the government to tackle coal and gas emissions.
Labor has pledged to lower emissions thresholds for the nation's 215 biggest polluters using the mechanism, which imposes the emissions cap.
