Controversial changes to Australia’s environmental protections have been decried as a product of “rotten, stinking politics”.

Hours before the federal budget and on the cusp of an election, the Albanese government has introduced a bill that could water down Australia’s main nature laws by removing the environment minister’s ability to revoke some past decisions.

“The economic and social impacts of changing a decision can be severe, putting jobs, communities and individual livelihoods at risk,” Environment Minister Tanya Plibersek told parliament on Tuesday.

“This bill strikes a balance between the important task of protecting our environment and the need to provide certainty.”

Crossbenchers and activists accuse the government of using the reforms to court voters in marginal Tasmanian electorates.

Under current laws an environment minister can change their approvals decision if new information comes to light. That could force a project to cease operations until a full assessment is done.

Approvals for the salmon industry in Macquarie Harbour have been under review by the minister since a 2023 challenge from conservationists.

Intensive fish farming in this area has caused oxygen levels to plummet, posing an existential threat to the Maugean skate, an ancient species of fish that is only found in two estuaries on Tasmania’s west coast.

But the reforms would prevent the minister from changing a decade-old decision, allowing salmon farming to continue in the electorate of Braddon, held by retiring Liberal MP Gavin Pearce on an 8 per cent margin.

Though Macquarie Harbour’s skate population levels have increased in recent years, there is still some way to go before they return to pre-2009 levels, University of Tasmania research has found.

Labor has also committed $28 million to improve oxygenation in the harbour, fund a breeding program and monitor the population.

The Greens have warned the bill’s ramifications go beyond one harbour.

“This will allow a carve out and a loophole – not just for the rotten salmon industry – but for the fossil fuel industry, for the logging industry, for the big polluters,” Greens Senator Sarah Hanson-Young told the upper chamber.

“This bill guts environmental protection in the name of the big corporations, in the name of stinking, rotten politics … it was put together in a hasty way so the Prime Minister has something to sell on his next trip down to Tasmania.”

Plibersek claimed the changes would only capture “a very small subset” of decisions.

Still, the Greens tried to send the legislation to an inquiry for further scrutiny but were unsuccessful.

Outside the chamber, 12 people were detained at Parliament House after three glued themselves to stairwells to protest against the bill.

The salmon industry has been under increasing pressure, with unprecedented mass deaths at farms in Tasmania’s south-east resulting in 6300 tonnes of salmon being dumped in February.

Crossbenchers, including Andrew Wilkie, Kylea Tink and David Pocock, have opposed the bill and urged the government to do more.

“(The Prime Minister) may talk a big game, but at every turn, he has undermined any progress on nature protection in this parliament,” Pocock said.

Prime Minister Anthony Albanese is understood to have scuppered 11th-hour nature law negotiations between Plibersek and the Greens, though he has denied this.

When asked about the fish industry, Albanese said his government would make “no apologies” for supporting jobs.

Opposition environment spokesman Jonno Duniam said Labor could not be trusted to protect salmon jobs, citing divides within his party.

“There are people who are not happy within the government, which makes me wonder whether they’re going to stick to their guns with this promise,” he said.

The bill is expected to pass by Wednesday, with support form the Coalition.

-AAP