Anthony Albanese says the referendum is the one and only chance Australia has to establish an Indigenous voice, ruling out future attempts should the proposal fail.
A poll released on Sunday showed the 'no' campaign still ahead a week out from referendum day despite a late gain in support for the 'yes' vote in the past month.
The survey, conducted for the Sydney Morning Herald by Resolve Strategic and based on responses from 4728 voters, showed 49 per cent opposed the voice and 38 per cent supported it, with another 13 per cent undecided.
When allowed only a referendum-style 'yes' or 'no' answer, 56 per cent of respondents opposed the change and 44 per cent were in favour.
Tasmania was the only state with a majority of 'yes' voters, the survey found.
With less than a week until voters go to the polls on whether to enshrine the voice in the constitution, the prime minister said on Sunday he would not seek to legislate the advisory body if the 'no' campaign won.
While he remains confident of success at the referendum on Saturday, Mr Albanese said the government would walk away from the voice altogether if the 'yes' vote did not succeed.
"We will continue to do what we can to listen to Indigenous Australians. We try that now. But Indigenous Australians are saying that they want (the voice) to be enshrined," he told ABC's Insiders program on Sunday.
"A 'yes' vote will be an important step towards reconciliation in this country."
Despite the 'yes' campaign trailing in the polls, Mr Albanese said a quarter of voters were yet to make up their minds.
The prime minister will lead a 'yes' campaign blitz across the country during the final days of the referendum, starting with doorknocking in the NSW town of Queanbeyan, just outside of Canberra.
"I'm hoping we vote yes because the debate here is whether Australia will enlarge ourselves, whether we're a country that looks for hope and optimism and for the future, or whether we shrink in on ourselves," he said.
"We're already undertaking measures (on tackling Indigenous disadvantage), but in my view, it won't be as effective as having a body, a voice to be listened to."
The Australian Electoral Commission said more than 2.2 million Australians have cast early votes in the referendum since pre-polling opened on Monday.
More than 92,000 people have voted at a mobile polling centre, including 19,000 in remote communities, while 1.9 million have applied for a postal vote.
While millions have already voted, Agriculture Minister Murray Watt said there were still larger numbers of undecided voters.
"Clearly, a lot of people have already chosen to vote and that is encouraging that people are getting out there and exercising their democratic right to have a say," he said.
"What's really important is that what it means is that there are many more millions of people out there who have not yet voted, and many millions of people who have made up their mind."
Assistant Indigenous Australians Minister Malarndirri McCarthy said she was optimistic about the referendum's success.
"I'm still very quietly confident that we can get this over the line," she told Sky News.
"I am deeply humbled by the support that we are getting on the ground."
Deputy Liberal leader Sussan Ley said the country would still have negative outcomes either way following the referendum.
"It's a lose-lose whatever the result is on Saturday," she told Sky News.
"It will be bad, divisive and unhappy for Australians the next day, so we do need to bring the country together
"It is just so important that the day after we we come together as a country."
