Fewer than one in five voters think Bill Shorten will win the election, yet around half intend to give his party either their first or second preference, according to the final Fairfax-Ipsos poll on the eve of the election.

The contradiction points to a looming dead heat that has lifted the potential for Saturday's election to deliver either a shock Labor win, a narrow Coalition victory, or a hung Parliament with no side commanding a majority in the House of Representatives.

A massive 27 per cent of voters remain intent on supporting Greens and other crossbench parties and independents, as support for the major parties threatens to erode further.

The tightness of the contest has the parties scrounging for every last vote especially in key marginal seats and prompted Malcolm Turnbull to use his final televised pre-election speech to the National Press Club to again plead with electors not to risk independents or a Labor protest vote, declaring: "Australians won't want to end up next week with a result they didn't see coming."

The final Fairfax-Ipsos poll of the 2016 election shows that with most Australians preparing to cast their votes Labor and the Coalition are locked in a 50-50 embrace based on second and subsequent preference flows recorded in the 2013 poll when Labor's electoral support had tumbled.

But when respondents were asked specifically which party would receive their second preference on Saturday, Labor edged into the lead at 51-49 - an identical outcome to that returned in the last two fortnightly Fairfax-Ipsos polls.

That represents a 4.5 per cent swing to Labor since 2013 and if registered uniformly across the country on election day, would be enough to safely install a Shorten Labor government.

The poll challenges a growing confidence observed on the government side over the past week and came as Bill Shorten continued to insist he could still win as he promised Australians that if they voted Labor, he wouldn't let them down.

Mr Turnbull used his speech to reinforce his message of stability, economic competence, and the dangers of a volatile global economy in which anything could happen – especially in the wake of last week's stunning Brexit decision to withdraw Britain from the European Union.

"These are times of great opportunity, but they are volatile times," a determined Mr Turnbull told the televised luncheon audience. "There is plenty of uncertainty around. You have got to approach that with a plan. You can't just pretend the world is some sort of tranquil environment where everything is going to be the same in six months, as it was yesterday. It is not ... that is why the critical choice on Saturday is to vote for a Liberal or National candidate because that is the only way to ensure that your vote counts towards a stable Coalition majority government and the delivery of our economic plan."

The 51-49 split in Labor's favour points to a major disconnect between voter expectations and voter intentions – perhaps fostered by a consensus in the political class of a likely Coalition win in spite of polling. Some 6 in 10 voters declared they expect Malcolm Turnbull to be returned, compared to just 17 per cent who think Bill Shorten will win.

But the nationwide survey of 1377 electors between Sunday June 26 and Wednesday 29, found the proportion of voters intending to vote for parties other than the majors remains high at 27 per cent – 13 per cent of which looks like going to the Greens, down fractionally since mid-June.

The high support for "other" portends an unmanageable Senate chamber after July 2, in which a plethora of disparate, if high-profile, independents could be elected along with the Greens. These include Derryn Hinch in Victoria, a Fred Nile-aligned candidate in New South Wales, Jacqui Lambie in Tasmania, Glenn Lazarus and or Pauline Hanson in Queensland, and as many as three Nick Xenophon Team senators in South Australia.

Of concern to Labor strategists, however, is Labor's persistently low primary support, which currently stands at just 33 per cent – equal to its poor return in 2013 when hounded from office by the rampaging Tony Abbott-led Coalition.

The Coalition primary vote sits at 40, having climbed by a statistically insignificant 1 per cent out of the 30s a fortnight ago.

Mr Turnbull remains the favoured option as prime minister with a lead on the preferred prime minister rating of 49 per cent to 35.

There is also a 16-point gap between the men on the separate assessment of their respective performance in their roles.

In Mr Turnbull's case, 49 per cent approve of the way he has done his job compered to a lower number of 41 per cent who disapprove, giving him a net approval rating of plus-8 per cent.

For Mr Shorten, it is almost the opposite with 42 per cent approval and 50 per cent disapproval, giving him a less comfortable approval rating of minus-8 per cent.

However, Mr Turnbull's net approval rating of plus-8 remains relatively low as prime ministers go, being slightly below that of Julia Gillard during the 2010 election campaign of plus-9.

John Howard by contrast had been plus-24 per cent when he won his final victory in 2004.

Mr Shorten is in an even worse position and has a lower approval rating than any opposition leader at this point in the electoral cycle.

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