Labor is blaming a law that was proposed and backed by the crossbench, including the Greens, for why the government is unlikely to announce a 2035 national emissions target ahead of the coming election.

Speaking after Prime Minister Anthony Albanese on the weekend refused to commit to releasing a number before Australians vote next year, Environment Minister Tanya Plibersek indicated one reason was that the government was awaiting advice from the Climate Change Authority on what the target should be.

In 2022 Labor passed legislation enshrining Australia's 2030 target — to cut emissions on 2005 levels by 43 per cent — but Greens and crossbenchers insisted on amendments that require the government to base future targets on input from the Climate Change Authority.

The ABC has learned that the authority believes it needs more time to model and consider the impact of Donald Trump's US election victory on global climate, energy and technology trends.

The agency, which has been dramatically expanded in terms of staffing and policy influence since Labor won the last election, is slated to begin a series of stakeholder consultations with business and climate groups next week.

At the same time, it has commissioned modelling work from the CSIRO, which was originally considering an emissions target for 2035 of between 65 per cent and 75 per cent.

However, sources familiar with the agency's deliberations told the ABC that Trump's return to the White House in January and his vow to gut the Biden administration's multi-trillion-dollar green energy and emissions reduction plans "changes everything".

"The playing field in which we were doing the economic modelling has shifted dramatically," one of the sources said.

Alongside a likely assault on the US Inflation Reduction Act (IRA) — President Joe Biden's flagship climate change and energy transition program — Trump is expected to withdraw the US from the Paris climate agreement.

If those threats come to pass, Australia may face a very different set of challenges in meeting its own targets.

"To get to a 70 per cent reduction in an IRA world is very different to getting to 70 per cent without an IRA because the technologies that are being underwritten by the US that could become commercially available look like being ripped away," the source said.

"So the level of ambition has changed."

Speaking on ABC's Insiders program on Sunday, Mr Albanese promised to release a 2035 target "sometime next year", pointedly refusing to deliver it before the election.

The opposition — which currently has no target for 2030 or 2035 — and Greens leader Adam Bandt used the remarks in Question Time to challenge Labor's climate credentials.

Acting Prime Minister Richard Marles hit back, saying the government's approach was putting both downward pressure on energy prices and helping the nation meet its emissions target by 2030.

He also slammed the Coalition's "$600 billion plan" to introduce nuclear power, saying it would delay the introduction of new energy generation in the grid for "many, many years to come".

Debate over Australia's climate target is likely to intensify next year when the country is expected to unveil to the world its official 2035 goal under the Paris climate agreement.

Other nations are also expected to update what are known as nationally determined contributions to keeping global temperature gains between 1.5 degrees and 2 degrees Celsius.

So far the UK has made the most prominent commitment. Prime Minister Keir Stamer last week committed Britain to an 81 per cent reduction by 2035.

The ABC understands Climate Change Authority chairman Matt Kean attended the United Nations climate summit in Baku, Azerbaijan, last week and met with more than 20 country delegations for talks on their plans for 2035 targets and when they might be released.

The message from those meetings was "that everything has changed", one source said.

Mr Kean told a Senate estimates hearing this month — prior to Trump's election victory — that coming up with a recommendation to the government required "a huge body of work".

"That work includes economic modelling and scientific modelling," he said.

"Obviously, we need to consider things in the geopolitical environment.

"We'll be making sure that our views are fully formed before we provide advice to the government and to the Australian parliament."

Mr Bandt asked Ms Plibersek on Monday why Labor was "now ducking and weaving on a pre-election target".

Ms Plibersek responded by saying she could "reassure" Mr Bandt that the "Climate Change Act that he voted for included within it a limitation that says the Climate Change Authority must provide advice before a 2035 target can be included".

"We are awaiting advice from the Climate Change Authority that is considering the important issue of setting a 2035 target which would be both ambitious and achievable," she said.

Labor's stance has shifted since June, when Climate Change Minister Chris Bowen told the ABC: "We're obliged to set our target by February next year, and we will."