Labor's signature 2030 climate target will pass after Greens leader Adam Bandt revealed the party will back the legislation, despite likening it to "bringing a bucket of water to a house fire".
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But Mr Bandt has declared the "fight starts now" to end the oil and gas industries in Australia, saying the Greens will pull "every lever" available to block new projects during the 47th parliament.
The bill's fate hinged on support from the Greens after Coalition leader Peter Dutton confirmed his intent to sink it this week.
Speaking during a highly-anticipated address to the National Press Club on Wednesday, Mr Bandt labelled the new government "neoliberal" and "now the party of the centre-right".
But he revealed the Greens will back Labor's attempts to legislate a 43 per cent emissions reduction target by 2030, despite arguing it was insufficient to avert catastrophic climate change.
"The Greens have improved a weak climate bill, but the fight to stop Labor opening new coal and gas mines continues," he said.
"In this parliament, the only obstacle to greater climate ambition is Labor.
"They will need to be clear eyed about the importance of this bill, and that this government is bringing a bucket of water to a house fire."
Labor's refusal to put a blanket ban on new coal and gas projects remained a sticking point for the Greens, who were adamant the 43 per cent 2030 target is too low.
"The climate crisis is caused by mining and burning of coal, oil and gas. You do not end the climate wars by opening more coal and gas mines," Mr Bandt said.
"At some point in our history, we have to say: it is time for no more coal and gas projects.
"Labor wouldn't leave a minimum wage or aged care nurse ratios to the market to decide. They shouldn't do it with a future of humanity, either."
Mr Bandt conceded Labor's win gave it a mandate, but stressed the Greens' strong showing gave it a mandate of its own.
"More important is our mandate from the planet and the laws of physics," he said.
"If Labor continues to open up new coal and gas, the planet will burn. That is the mandate that we all need to listen to."
The Coalition's stance meant Labor will be forced to rely on the Greens and one other senator, likely the ACT's David Pocock, to pass the bill in the upper house.
But with the new government flatly ruling out a moratorium on coal and gas, Mr Bandt rejected suggestions the party had lost leverage by backing the bill.
"This is round one," he said.
"The penny hasn't really dropped with the government yet [on] just how much the rest of the world and the Australian public wants climate action, and wants them to stop opening new projects.
"We will use every lever at our disposal in this parliament, and on the streets with the movement, to make that happen."
Mr Bandt's decision was reached after protracted discussions on Tuesday.
The Greens failed to reach a consensus during a party room meeting that morning, with Mr Bandt forced to reconvene an urgent evening sitting to finalise the party's stance.
"Of course, during that, there are different positions put forward. I would be disappointed if that wasn't the case," Mr Bandt said.
"The way that you get good outcomes is by having different positions put there, proposed, tested, and refined and we went through that process."
'End the climate wars'
Labor made the target a centrepiece of its successful campaign, with Prime Minister Anthony Albanese pledging to "end the climate wars" during his election night acceptance speech.
Speaking after the announcement, Mr Albanese said he was confident the bill would pass both houses and urged the opposition to reverse its stance.
"This is an opportunity for the whole of the parliament to be on the right side of history," he said.
Mr Albanese said the government had not given the Greens any assurances on the Environment Protection and Biodiversity Conservation Act, but accepted there would be amendments.
"I'd give everyone who's prepared to vote for moving forward, even though it's not everything that they would want, credit for doing so," he said.
"Mr Bandt ... [has] been prepared not get everything that he wants, and not get a whole lot of things that they want."
The bill was introduced on Labor's first full parliamentary sitting day, and the government has the numbers to pass the bill in the lower house.
But Climate and Climate Change and Energy Minister Chris Bowen has consulted a number of pro-climate action crossbenchers in both houses to push it over the line.
Speaking to the ABC on Tuesday morning, independent MP Zali Steggall said ongoing discussions had already produced "some movement" on a number of amendments to strengthen the bill.
That included on references to temperature goals set out in the Paris Agreement, stronger accountability in terms of government reporting to parliament, and more certainty on labelling the 43 per cent target a "floor" rather than a "ceiling" over emissions reduction, she said.
"A number of the amendments, they appear to be receptive to them. Of course, they have to take into the party room and discuss them," she said.
"But I have to give credit. Chris Bowen and his team have been incredibly consultative with us and very open to improving the legislation."
Dutton goes nuclear
Working through the opposition's stance at its own partyroom meeting on Tuesday, Mr Dutton confirmed his intent to sink the bill.
But in an attempt to placate the moderate wing of the party, he said the opposition would announce an increase on its existing 27-28 per cent target before the next election.
Part of that will be a review into the viability of nuclear energy, raised by the Nationals after their May defeat but never seriously pursued during nine years of Coalition government.
Mr Dutton said it was "high time that Australia had an honest and informed debate" about pivoting to nuclear energy.
Moderate Liberals Andrew Bragg, Bridget Archer and James Stevens all spoke up in the party room meeting about the need for more ambitious policies.
Senator Bragg emerged from the meeting assured that the Coalition would take a higher medium-term emissions reduction target to the next federal election.
"We were given a strong message on emissions by the electorate," Senator Bragg told The Canberra Times.
"We will now have, throughout this term, a stronger and more ambitious emissions reduction policy.
"I think we are heading in the right direction by committing ourselves to a new emissions reduction policy."