Supporters of Peter Dutton say the Home Affairs Minister is leaning towards challenging Malcolm Turnbull for the prime ministership and has the numbers to win, amid a crisis over energy policy and a horror new poll showing support for the Coalition has slumped.

Mr Dutton has spent the weekend taking soundings among Liberal MPs, leaving close colleagues with the clear view that he believes the government is now in an unwinnable position.

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All indications were that Mr Dutton was ready to run for the leadership, they said, in another sign of a Coalition meltdown with conflicting claims over support for rival camps ahead of a policy showdown in the Coalition party room on Tuesday.

An exclusive Fairfax-Ipsos poll shows the Coalition has suffered a horror slump in its primary vote from 39 to 33 per cent over the past month amid open disputes on energy and speculation over the leadership.

In its worst result since early last year, the Coalition now trails Labor by 45 to 55 per cent in two-party terms in a result that would cost the government more than 20 seats at a general election.

The moves come as Mr Turnbull’s supporters rally behind the Prime Minister to back his energy policy and his leadership, insisting he has majority support despite open conflict with his predecessor, Tony Abbott.

One cabinet minister said MPs were increasing their support for Mr Turnbull due to concerns the elevation of Mr Dutton to the leadership would be followed by the restoration of Mr Abbott to the cabinet, either in the defence or home affairs portfolio.

Another cabinet minister was scathing about the jostling for a spill at the expense of government unity, while a third said there was no majority support to force a change.

One Liberal estimated the chances of a spill at 50:50 but said “the odds are increasing” not only because of the dispute over the National Energy Guarantee but the wider argument over the government’s direction.

No formal headcount has been conducted and supporters of the Prime Minister say that he still enjoys the support of the party room, but several days of frenetic phone calls among MPs has agitated the party and destabilised the government.

The fact that Mr Dutton took 24 hours on Friday and Saturday to respond to leadership speculation led MPs to predict he would move at some point if Mr Turnbull could not manage the discontent in the party room.

Mr Turnbull brought cabinet ministers to Parliament House on Sunday night to discuss policy over dinner, ahead of a formal meeting on Monday night to finalise a package to go to the party room on Tuesday.

One supporter of Mr Dutton noted the minister’s tweet of support for Mr Turnbull on Saturday morning had avoided any pledge not to challenge the leader.

“He supports the Prime Minister 'till the moment he’s challenging him,” the MP said.

With the situation fluid on Sunday night, some Liberals said a leadership change was increasingly likely while others flatly said they had “no interest” in a spill.

One Liberal disputed claims that marginal seat MPs were in favour of a shift to Mr Dutton, pointing to several in NSW and Victoria who would fare better at the federal election with Mr Turnbull as leader.

In a federal Liberal party room of 85, those supporting Mr Dutton estimate he has a majority comfortably above the 43 votes required to win. While he is the candidate of the party’s conservative wing, he has also won over some moderates who are despairing at Mr Turnbull’s leadership.

Some of the conservative members of the Coalition backbench already were campaigning against the National Energy Guarantee, but Mr Turnbull’s sudden change to the policy on Friday alienated more of his colleagues.

“Malcolm likes to talk about how he runs good cabinet processes, but that was a captain's call and it was desperate,” said one of his cabinet ministers.

“Rather than fix the problem of the NEG he has exacerbated it. The NEG is now dead.”

The Prime Minister is expected to take the revised NEG to the Coalition party room for approval on Tuesday.

“It doesn’t matter what the NEG turns out to be now,” said a conservative Liberal.

“It’s broader than that – it’s now about our direction, our base, and our personnel.”

Mr Turnbull has lost ground to Opposition Leader Bill Shorten on key measures of voter satisfaction, narrowing the gap between the two men when Australians are asked who they prefer as prime minister.

The fall in support for the Coalition was matched by a boost for minor parties including Pauline Hanson’s One Nation rather than a gain for Labor, which saw its primary vote increase marginally from 34 to 35 per cent.

Support for the minor parties rose from 15 to 19 per cent while the Greens saw an increase in their primary vote from 12 to 13 per cent.

A narrow majority of voters back the NEG, with 54 per cent in favour while 22 per cent are against it and 24 per cent are unsure.

Support for the flagship energy policy is strongest among Coalition voters, at 64 per cent, but the scheme is also backed by 59 per cent of Labor voters and 44 per cent of Greens voters.

Even so, 56 per cent of all voters believe the government is doing too little to address climate change amid the argument over the scale of the cuts to greenhouse gas emissions in the new scheme.

In a sign of discontent among conservative voters, the number who believe the government is doing too much on climate change has jumped from 7 to 13 per cent of all respondents since Fairfax-Ipsos asked the same question three years ago.

The slump in the Coalition’s primary vote is expected to trigger a storm over the findings, as Mr Turnbull and his allies warn against placing too much faith in the polls.

“The poll is robust and reliable, conducted to the same methodology as used for the Fairfax-Ipsos polls since 2014,” said Ipsos public affairs director Jess Elgood.

“As with our previous polls in 2018, our sample of 1,200 means that the aggregate findings are statistically reliable to plus or minus 2.9 per cent, at the 95 per cent confidence level.”

The result in two-party terms, with the government lagging Labor by 45 to 55 per cent, is based on preference flows at the last election.

The result was the same when respondents were asked how they would allocate their preferences, a dramatic gain for Labor compared to the dead heat for the two major parties on this measure in the last Fairfax-Ipsos survey.

In a personal blow to Mr Turnbull that matches the shift against his government, his support as preferred prime minister has fallen from 57 to 48 per cent over the last month, while Mr Shorten has improved his standing from 30 to 36 per cent.

The gap between the two leaders as preferred prime minister has shrunk to 12 percentage points, the closest it has been since May last year.

The proportion of voters who approved of Mr Turnbull’s performance fell from 55 to 46 per cent over the last month while those who disapproved rose from 38 to 48 per cent.

Mr Turnbull’s net approval rating – the difference between those who approve and disapprove of his performance – plunged from 17 percentage points last month to minus 2 points in this poll, his first negative result since last November.

At 33 per cent, the Coalition’s primary vote is six percentage points below its result in the last Fairfax-Ipsos survey and nine percentage points below its result at the last election.

Labor’s primary vote of 35 per cent is up slightly from the 34 per cent result in the last poll and is the same as its result at the last election.

Voters increased their support for the Greens from 12 to 13 per cent but the strongest gains were among other political parties, a group that includes Pauline Hanson’s One Nation.

The latest survey finds 19 per cent of voters give their first preference votes to other parties, up from 15 per cent in the last survey.

The Fairfax-Ipsos survey of 1200 respondents was conducted from August 15 to 18 and has a margin of error of 2.9 per cent.