The Greens will offer critical support to a climate bill that will legislate the government's 2030 emissions reduction target, giving it the numbers it needs to pass in the Senate.
Labor has introduced a bill to enshrine its 43 per cent emissions reduction target into law and tighten up reporting schemes to track progress towards the target.
Greens leader Adam Bandt has told the National Press Club that his party will back the bill, giving it the votes needed to pass.
Mr Bandt said he remained "bitterly disappointed" the government would not ban new coal and gas projects, and that the party would vote to send the bill for inquiry, where they hope to prove Labor's climate policies would fail to meet a legislated 43 per cent target.
"Labor might be holding out now, but their position is ultimately untenable, and they can't go to upcoming climate summits, vowing to open new coal and gas projects and expect to be taken seriously," he said.
Mr Bandt said the party will now push to shut down future projects by amending the safeguard mechanism, which penalises big polluting companies that go over a set carbon emissions ceiling.
Climate Change Minister Chris Bowen shut down any prospect of a coal and gas moratorium being introduced through the safeguard mechanism, saying the government would implement its election plan "without alteration".
Mr Bowen said it will begin consulting on the emissions lever later this month.
The government did not have the numbers in the Senate to pass its climate target bill without support from the either the Coalition or the crossbench.
The Coalition determined it would oppose the bill yesterday, although some of its MPs and at least one senator are considering crossing the floor to support it.
Without the Coalition's support, the government needed the Greens' backing to have any chance of legislating its target.
The government will also need the support of at least one other senator — independent senator David Pocock has already indicated he will give it his support.
Australian Chamber of Commerce and Industry boss Andrew McKellar said passing the bill would send a clear and welcome signal to the market in its transition to clean energy.
"This is a missed opportunity for the Opposition. The announcement today demonstrates that the climate wars are over. This must act as a moment for unity of purpose," Mr McKellar said.
Prime Minister Anthony Albanese challenged the Coalition to "end the climate wars" and give its support to the bill.
"The parliament is about to, after a decade of inaction and denial and delay, to move forward," Mr Albanese said.
"This is an opportunity for the whole of the parliament to be on the right side of history."
Greens say Labor will have to shift on coal and gas moratorium
Mr Bandt said his party would continue to fight new coal and gas projects, despite agreeing to give Labor's bill passage.
"This is round one, there is three years of this parliament," Mr Bandt said.
"Labor's position is ultimately untenable ... this is increasingly becoming a deal breaker around the world."
For a decade, Labor and the Greens have held bitter memories over the Greens decision not to back Labor's Carbon Pollution Reduction Scheme in 2009, which was ultimately defeated in parliament.
Labor has argued that the Greens share some of the blame for a so-called decade of climate inaction that followed because of their decision to oppose the CPRS.
The Greens had long held that the policy wasn't going to work, and would have locked the government into insufficient emissions targets that would not have seen any improvement for 25 years.
The climate target bill, while largely symbolic because the government does not require the laws to achieve its 43 per cent target, was seen as a litmus test for how the two parties would likely interact on climate change in the term to come.
