After a fortnight of damaging infighting and supercharged leadership speculation, former frontbencher Sarah Henderson said she could not continue to "back things the way they are" ahead of a key partyroom meeting in the coming week.
"I do have to say really honestly, I do think Sussan is losing support," the senator told Sky News on Friday.
"But I do believe in miracles."
Asked whether the party can turn itself around with Ms Ley at the helm, Senator Henderson took a long pause before reiterating she could not support the "way things are".
"I'm not in the business of throwing anyone under the bus, I'm stating the bleeding obvious, we are in a dire situation," she said.
"The infighting has been terrible and I'm terribly sorry about what's been going on in the Liberal Party."
Senator Henderson, who was dumped from shadow cabinet after Ms Ley took over the Liberal leadership, commended the opposition leader for calling a series of meetings as a "significant step forward" in deciding a policy position on energy and climate.
"I vehemently oppose net zero in all of its guises, it's sending our country backwards," the conservative senator said.
After weeks of internal brawling, Liberal members are shortly due to decide a position on retaining or dumping an existing goal of achieving net-zero greenhouse gas emissions by 2050.
A partyroom meeting will be held on Wednesday and shadow cabinet will meet to formalise their position the following day.
But even if the Liberals land a cohesive plan amid fierce internal divisions, they will still need to strike an agreement with junior coalition partner the Nationals, who have already elected to drop the formal net-zero target.
Former Liberal leader John Hewson has delivered a withering assessment of Ms Ley and the party she leads in the midst of the fractious policy debate.
"She hasn't shown any clear strategy, or any strong capacity in terms of leadership," he told AAP.
Mr Hewson, who let his membership lapse in 2019 because of concerns about the party's record on climate change, said the opposition was devoid of serious policies because its members had little experience outside politics.
"They haven't got people with significant business experience ... I don't think that they've got people who are policy wonks in economic policy," he said.
"You can't just keep being negative and hoping to win on criticism, as (Tony) Abbott did."
As opposition leader, Mr Hewson took a highly detailed promise of economic reform to the 1993 federal election, which the coalition roundly lost to Paul Keating's Labor government.
"I'd really like to see Sussan be given a fair run with everyone pitching in and doing a proper policy job," he said.
Mr Hewson was also highly critical of West Australian MP Andrew Hastie, who is widely considered a potential leadership contender and has been a vocal critic of the nation's climate targets.
"He's been sold a bit of a dump by the right of the party," the former Liberal leader said, arguing Mr Hastie's criticism of Australia's immigration program was unlikely to be popular in the broader electorate.
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