Liberal MPs have launched a rearguard action to salvage a commitment to net zero emissions, with one warning the party “will pay dearly in city electorates” and undermine Australia’s international reputation if the Coalition abandons the target.

The South Australian senator Andrew McLachlan said the internal campaign to preserve a net zero emissions policy was “not over” despite a growing expectation that the Liberals will follow the Nationals in dumping the climate goal.

McLachlan and moderate Liberals Andrew Bragg, Jane Hume and Maria Kovacic were on Tuesday publicly resisting the right faction-led push to junk not just the Scott Morrison-era pledge to net zero by 2050 – but any firm commitment to carbon neutrality.

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Tim Wilson also rejected suggestions his colleagues should fall into line with the Nationals, saying the Liberals were not the “National party-lite” and would determine their own position.

A special Liberal party room meeting is expected to be convened later this month as Sussan Ley attempts to revolve a policy brawl that has become a major threat to her leadership.

While dumping net zero would stave off a leadership challenge, possibly from right-wingers Angus Taylor or Andrew Hastie, it would provoke serious pushback from MPs who helped win her the top job.

Retaining a commitment to net zero emissions is a line in the sand for some Liberal MPs, who would consider agitating to split from the Nationals if the policy was abandoned entirely.

Bragg said the Liberals were better off sticking with the Nationals but noted “there’s a reason you have divorce laws”.

McLachlan, the most pro-climate Liberal in Canberra, warned colleagues about the potential cost of abandoning a net zero commitment, including at the ballot box.

Scrapping net zero would take the Liberals further back on climate policy than it was under Morrison and Peter Dutton, whose emissions policies – or lack thereof – were considered major factors in the loss of city seats to Labor and teal independents at the past two elections.

“Those wanting to run away from our global commitments seem to have convinced themselves that they can do so without cost,” McLachlan said.

“If we retreat from achieving net zero, we will pay dearly in city electorates. Our reputation as a nation that keeps its promises will be diminished. Our Pacific friends will be betrayed.”

Bragg, Kovacic and Hume all cited the need to maintain Australia’s obligations under the Paris agreement as justification for keeping net zero emissions.

“Well, the Paris agreement is the red line here. You’ve got to be in the Paris agreement because if you weren’t, then you’d be in a group of countries like Iran and Libya and maybe two or three others,” Bragg told ABC News Breakfast.

Kovacic said any break with the Paris climate agreement would hurt Australia’s standing around the world, and hurt the economy.

Bragg is open to a compromise in which the Coalition commit to reach net zero emissions after 2050, noting for the second day in a row that the text of the Paris agreement said net zero should be achieved this century.

However, that position would be a breach of Australia’s obligations under Paris, which requires that countries do not go backwards on their commitments.

The Albanese government has committed Australia to net zero emissions by 2050, with the interim goals of 43% by 2030 and 62% to 70% by 2035, compared with 2005 levels.

The climate change minister, Chris Bowen, said net zero emissions by 2050 was not a “political construct … it’s a scientific requirement”.

“The LNP appears to think they know better (than the world’s scientists),” Bowen said.

“They know better than the IPCC, which said if you want to keep the world to 1.5 degrees of warming, you need net zero by 2050. Not a nice-to-have, not a good-to-have, it’s essential. Now, that used to be bipartisan in Australia.”

At a joint party room meeting on Tuesday morning, Liberals and Nationals MPs were briefed on the process for settling the Coalition’s net zero position before Christmas.

The shadow energy minister, Dan Tehan, said his policy review process was expected to wrap up “imminently”, paving the way for a special Liberal party room meeting, possibly to be held on 23 November, before the final sitting week of the parliamentary year.

Once Tehan’s group reports to the Liberal leadership team, Liberal members of the shadow cabinet will consider the findings before all Liberals are given the chance to thrash out the issue.

Once that process is done, Ley and the Nationals leader, David Littleproud, are expected to meet to finalise a joint Coalition policy, which is expected to see net zero policies dumped.

Conservative South Australian Liberal MP Tony Pasin told the meeting he believed the two sides of the debate “were closer than what people thought”