A Liberal backbencher has declined to endorse Sussan Ley as leader, declaring she is “losing support” amid dire opinion polls and bitter infighting about net zero emissions.

The conservative Victorian senator Sarah Henderson told Sky News on Friday morning she “can’t support things the way they are at the moment” but was hopeful the opposition could turn the situation around.

Asked if Ley could turn the situation around, Henderson said: “I don’t know.

“I don’t support the way things are, and I am desperate for us to do better.

“I think there’s increasing concern in our party as to the way we are going … the infighting has been terrible.”

When pushed on whether she thought things could be better under Ley, Henderson paused before replying: “Well … I am just going to say at the moment that I cannot support the way things are.”

She conceded that the comments were not an endorsement of Ley.

Sign up: AU Breaking News email

She later said she was not calling for a new leader before reiterating her view that Ley was “losing support”.

Speaking to reporters in Parliament House straight after the Sky interview, Henderson doubled down on her comments.

“At the end of the day, we need to do better and I’m very hopeful that we can turn this ship around,” she said. “I think a lot of my colleagues are very concerned about the way things are going.

“We know things are dire at the moment and I can’t pretend that things are going well.”

Henderson is a factional opponent of Ley’s who was dumped from shadow cabinet after the election, meaning the criticisms are unlikely to come as a surprise to the leader and her allies.

But the comments will nevertheless inflame the internal tensions before a series of crunch meetings next week to determine the Liberal party and Coalition’s position on net zero emissions.

Despite protests from Liberal moderates, Ley is expected to follow the Nationals in dumping net zero emissions as a target amid concern among senior colleagues that the term has become “poisoned” in the political debate.

The two leading contenders to replace Ley, Angus Taylor and Andrew Hastie, both support abandoning the target, putting pressure on the leader to follow suit.

skip past newsletter promotion

Sign up to Breaking News Australia

Get the most important news as it breaks

Privacy Notice: Newsletters may contain information about charities, online ads, and content funded by outside parties. If you do not have an account, we will create a guest account for you on theguardian.com to send you this newsletter. You can complete full registration at any time. For more information about how we use your data see our Privacy Policy. We use Google reCaptcha to protect our website and the Google Privacy Policy and Terms of Service apply.

Henderson refused to answer if Hastie or Taylor could do a better job – but the senator strongly supports ditching the net zero policy.

The pressure on Ley’s position has also intensified after the Coalition’s primary vote slumped to a record-low 24% in the latest Newspoll – just nine points in front of Pauline Hanson’s One Nation.

Ley’s own personal approval rating crashed to minus 33, according to the poll published in The Australian.

The leader this week insisted her position was safe while Taylor and other leading conservatives ruled out a challenge this year.

The Liberal party’s position on net zero emissions will be formalised at a meeting of the Liberal shadow ministry in Canberra next Thursday, which will follow a party room meeting the day before to endorse a “set of principles” on climate and energy.

Three senior Liberals and Nationals will then thrash out a joint position, which will be put to a virtual Coalition meeting on Sunday 16 November.

In an opinion piece published in the Australian Financial Review on Friday, the shadow energy minister, Dan Tehan, set the stage for the Liberals to dump the Scott Morrison-era pledge to reach net zero emissions by 2050.

“We urgently need a reset in how we think about energy and emissions reduction, shifting from doomsday narratives towards rational policies that prioritise strategic investment in R&D, and innovation,” Tehan wrote.

“The political debate over climate change needs a reset.”