The Greens leader, Richard Di Natale, has urged supporters in Wentworth to “take note” of Kerryn Phelps’ progressive positions on climate change and refugees when they cast their ballots on Saturday, in a clear signal to preference the high-profile independent ahead of Labor.

Di Natale told Guardian Australia the government was clearly at risk of losing Malcolm Turnbull’s former seat, and Labor was “running dead” in the contest, so in that context “people can vote Green and choose Kerryn over yet another Liberal backbencher”.

The Greens leader urged rusted-on supporters to vote for the party’s candidate, Dominic WY Kanak, and then “take note of Kerryn’s progressive views on refugees and climate change, which are a welcome change from both the major parties”.

“The Wentworth byelection has become a referendum on climate change and refugees and is a unique opportunity to send a message to the Liberals who don’t deserve to govern,” he said.

The Greens preferenced Labor above Phelps on their how-to-vote card for the contest, but now both the current federal leader and a former leader of the Greens, Bob Brown, have suggested supporters ignore those instructions and instead rank Phelps ahead of Labor’s Tim Murray.

The signal in the final 48 hours of the contest reflects a judgment by the Greens federally that the election of Phelps to the federal parliament, given her clear statements on refugees during the byelection contest, would be beneficial in trying to secure a breakthrough for asylum seekers on Nauru.

In the run up to the Wentworth contest, both the major parties have shifted ground, with Scott Morrison raising the prospect asylum seekers could be resettled in New Zealand and Bill Shorten flagging new procedures for medical transfers – but there is no breakthrough yet.

MPs in both the major parties, the Greens and a number of cross benchers are working actively with refugee groups and the medical community to push for an outcome that would see children and families removed from Nauru.

The GetUp how-to-vote, for those who want to vote 1 Green, also modifies the Greens recommendation and puts Phelps ahead of Murray.

If Phelps comes third after Murray, her preferences are expected to flow to the Liberal candidate, Dave Sharma, more strongly. If Labor comes third, its preferences are expected to flow to Phelps, which could catapult her to victory.

Internal Liberal polling and other polls show the Liberal primary vote has collapsed and Phelps has surged to about 25% support, while Labor is at about 21%.

Out on the hustings on Friday morning, Phelps declared both the prime minister and the Australian newspaper “must have failed comprehension at primary school” after the newspaper warned she was “open to tearing down the government” on the final day of the campaign.

The story, which was seized on by Scott Morrison on Friday, was headlined “After Wentworth, Phelps open to tearing down the government”.

The newspaper quoted her saying that she had put on the record that she thought governments should run their full term but left open the possibility of joining a no-confidence motion.

“I think we’d have to see the context of what that was, but my intention would not be to bring the government down before its term was complete,” she said to the Australian.

“I think it should be in the hands of the Australian people to decide who their next government was going to be and that should happen at the next general election.”

Asked by Guardian Australia whether she would “tear down the government”, Phelps laughed and said: “I think they would have failed comprehension at primary school.”

She reiterated her stance that she would vote on legislation on its merits and that her intention was for the government to serve its full term.

“I believe that governments should run their full term and I also believe prime ministers should run their full terms,” she said. “I am going to offer strong and sensible leadership.”

She has previously told Guardian Australia that a decision on a no-confidence motion would depend on how bad the behaviour of the government is, but her intention was for the government to serve its full term.

Phelps also pointed out that there were now five independents and no single independent could determine the future of the government.

Morrison was quick to seize on the Australian’s headline on Friday morning.

“[In] the last 24 hours, we have heard the leading independent candidate has said she could not guarantee not bringing down the government on a vote of confidence,” he said.

“Now, that is serious stuff. They’re her own comments, they’re her own observations. She has not ruled out bringing down the government if she is elected on Saturday. Now, that is the definition of instability.”

The government is pessimistic about the outcome of Saturday’s contest. The Nationals’ Darren Chester today all but conceded defeat in the Wentworth byelection while Morrison has warned voters if they elect an independent it’ll make an uncertain and unstable government even worse.

“I don’t think the result is going to be good for us in Wentworth,” Chester said. “I think it’s important to remember how we got to Wentworth,” Chester told ABC radio while being quizzed about a potential Nationals leadership spill.

“I don’t think the Wentworth byelection will be good for the government. I think we’re about to get a real-life opinion poll on what Australians think of political parties that undermine their leaders and change leaders mid-stream.”

Morrison was asked whether he is praying for a miracle in the Sydney seat. “I pray often about many things,” he said.