Support for both Julia Gillard and her government has slumped, wiping out most of the gains made since the carbon tax was introduced last year and raising the chances that she could be replaced by Kevin Rudd.
Tony Abbott now leads Ms Gillard as preferred prime minister for the first time in seven months, but Mr Rudd declared on Sunday that he would not be drafted into the Labor leadership.
The Herald/Nielsen poll found the gap between Ms Gillard and the former prime minister has grown, with Mr Rudd favoured by 61 per cent of respondents to just 35 per cent for her.
The ALP is gripped by internal tensions over the possibility, but Mr Rudd, who fuelled speculation last week with criticism of the mining tax, used a sixth high-profile TV appearance in a week to dismiss speculation.
''A couple of weeks ago I said everyone should take a cold shower,'' he told Sky News Agenda. ''Last Friday I said they should have an ice bath. It's time this debate was put into cryogenic storage.''
Labor's support, which had climbed into the mid-30s, has now collapsed, plunging it back towards landslide-losing territory were an election held now.
Its primary vote stands at just 30 per cent, a dip of 5 points since the last survey in December and a mere 4 points above its nadir of 26 per cent in May 2012.
Support for the Coalition rose 4 points, taking its primary vote to 47 per cent - its highest level since just after the carbon tax began in July 2012. Greens support held steady at 11 per cent.
On a two-party-preferred basis, Labor's support languishes at 45 per cent to 55 per cent for the Coalition, according to voter feedback on the direction of second preferences.
Based on preference flows from the 2010 election, the two-party split is 44/56 in favour of the Coalition - a swing towards the Coalition.
It was a bad sign for the government in an election year, the pollster John Stirton said.
''It confirms that the trend to Labor that ran from May to November last year and appeared to stall over Christmas is now heading in the opposite direction,'' he said.
Crucially, in terms of Ms Gillard's command of the Labor leadership, Mr Abbott has overtaken her in the preferred prime minister stakes with his support leaping by 9 percentage points to 49 per cent compared with Ms Gillard on 45 - down 5 points.
Labor strategists have previously pointed to her superior popularity as an important reason to retain her as leader.
The poll follows a terrible fortnight for Labor in which Mr Rudd returned prominently to the airwaves and the Treasurer, Wayne Swan, admitted his mining tax had raised almost no revenue.
Fewer than one in four voters now support the mining tax in its current form, with two thirds of voters in favour of either dumping it or making it stronger.
The national poll of 1400 voters was carried out between Thursday and Saturday.
Approval/disapproval ratings tell a similar story of woe for the embattled Prime Minister.
The snapshot of voter sentiment coincides with a Galaxy Poll published by News Limited newspapers on Sunday that showed female voters, thought to be Ms Gillard's secret weapon against Mr Abbott, were walking away, with 36 per cent indicating support for the Prime Minister.
Mr Stirton said it was possible that women may have led the charge away from Ms Gillard.
''There is some evidence that the fall in Labor's vote was greater among women than men but we will need another round of polls to confirm this,'' he said.