A reputed rival to Liberal leader Sussan Ley is refusing to categorically rule out challenging her, while denying he plans to do so.

Ahead of a crucial meeting of Liberal MPs and senators on Wednesday, party insiders say they will likely water down Australia’s climate ambition if they return to government, while retaining a commitment to reaching net zero carbon emissions at some point.

Moderates, such as NSW senators Andrew Bragg and Maria Kovacic, had said they will quit the frontbench if net zero is ditched, while conservatives, such as shadow defence spokesman Angus Taylor, want an end to the policy.

On Tuesday, Taylor said he wouldn’t pre-empt the outcome of the meeting but would not support “economically destructive and unachievable targets”.

“So we won’t be supporting Labor’s failed net zero plan,” he told Nine’s Today Show.

“That I can guarantee.”

Australia signed up to the Paris accord in 2015 under then-prime minister Tony Abbott, promising to limit its greenhouse gas emissions as part of a global push to tackle global warming.

Six years later, the Morrison government set a target of net zero emissions by 2050. Labor has since set more ambitious climate goals including a 62-to-70 per cent reduction in carbon pollution by 2035.

Debate over the Coalition’s climate policy restarted in earnest after Labor’s May election win, and the issue now threatens to engulf Ley’s leadership.

Taylor was last week spotted dining in Canberra with a splinter group of conservatives who have been vocal in their criticism of net zero. Among them was putative leadership challenger Andrew Hastie.

It sparked rumours that Taylor or Hastie might be manoeuvring to challenge Ley pending the outcome of this week’s climate policy discussions.

Taylor brushed off suggestions he was planning a coup, but was less than effusive in his support of his leader.

“That’s just not right,” he said.

“I’m focused on making sure we’ve got the policies we need coming together to hold this government to account and to be contestable at the next election.”

Offered the opportunity to categorically rule out a challenge, he responded: “It’s not something we’re planning.”

Labor frontbencher Amanda Rishworth, being interviewed on the program alongside Taylor, was asked if she found his response convincing.

“Well, no,” she said.

The Liberals’ net zero debate comes after their Coalition partner the Nationals announced they would ditch a formal climate target and instead tie emissions reductions to an average of OECD countries.

University of Queensland climate and environmental law expert Justine Bell-James said any move to weaken Australia’s targets would be in breach of the Paris accord.

“Under the Paris agreement countries have to make these pledges every five years,” she said.

“Because of this mechanism that they call the ratchet mechanism, each successive one needs to be an increase in ambition.”

Latrobe University climate law expert Julia Dehm agreed, saying a future government would “certainly” be in breach of the Paris agreement if it went back on its promises.

Dehm said a ruling from the International Court of Justice in July that all countries had a legal obligation to tackle the “urgent and existential threat” of climate change was an additional barrier to watering down Australia’s climate targets.

“There is the potential for states to take Australia to the ICJ alleging that it hasn’t fulfilled its international climate obligations,” she said, adding that a weaker emissions reduction goal would also cause reputational damage for the government.

-AAP