A key Labor election promise hangs in the balance as the Greens meet to discuss their stance on climate laws.
The minor party did not reach an agreement on the issue on Tuesday morning, forcing a second meeting to be called later in the day.
Labor's bill, which will enshrine an emissions reduction target of 43 per cent by 2030 and net zero by 2050, needs the support of all 12 Greens MPs plus one crossbencher to pass the Senate.
A meeting of Liberal and Nationals MPs and senators on Tuesday affirmed opposition to the bill.
Negotiations between Greens leader Adam Bandt and Climate Change Minister Chris Bowen have been ongoing after the Greens expressed concerns with the bill.
They have called for more ambitious climate targets and for an end to coal and gas projects.
But the government insists Australian voters gave a mandate for the 43 per cent emissions reduction target.
The target is consistent with Australia's international obligations, Mr Bowen told parliament.
Greens MPs have previously described the bill as "pathetic".
Tuesday's second meeting in Canberra will run as long as necessary to reach a final decision and a majority vote will be sought if consensus cannot be reached.
Opposition Leader Peter Dutton told the coalition joint partyroom meeting the government itself had stated legislation was not essential to put in place the 43 per cent target.
The coalition will develop its own climate policy for the next election, which will include updated targets beyond the existing 26 to 28 per cent cuts.
The potential for how nuclear energy could fit into the energy mix would also be explored in a review of coalition policy, Mr Dutton said.
Moderate Liberal senator Andrew Bragg told AAP the party was in a "good position" to develop a climate policy over the next two-and-a-half-years in opposition.
Senator Bragg has previously said he was considering crossing the floor on the issue.
"We need to develop a policy which is serious on emissions reduction, 2030, 2035 and the additional years short of 2050, because we already have a very good policy for 2050," he said following the partyroom meeting.
"The most important thing I can do as a Liberal Party senator is to try and encourage my party to adopt a strong and credible policy on emissions reduction."
Senator Bragg said he would set out his arguments on the bill in a report stemming from a Senate inquiry, which is due to be handed down at the end of the month.
While some MPs expressed concerns about the coalition's opposition to the government's climate bill, none told the meeting they would vote against the party line.
Independent MP Helen Haines intends to seek an amendment to the government's proposal to ensure regional Australia benefits from action on climate change.
Her amendments would require the Climate Change Authority to ensure any measures responding to climate change should have economic, employment and social benefits.
Dr Haines also wants the regions to be explicitly considered when new emissions targets are set.
"It means that no government can get away with a climate policy that does not specifically address the unique circumstances of and opportunities for regional Australia," she said in a statement.
"This (energy) transition will happen primarily in the regions, so it only makes sense that our climate policy keeps a special focus on the regions."