Tasmanian senator Jacqui Lambie has launched a scathing attack on the Albanese government over its Indigenous Voice campaign, as polls show a further tumble in the Yes vote.

Opposition Leader Peter Dutton also urged Prime Minister Anthony Albanese to abandon the October 14 vote, as a Resolve Political Monitor survey, published in Nine newspapers on Monday, showed only 43 per cent of voters supported a plan to enshrine an Indigenous Voice in the constitution, down 20 percentage points from a year ago.

The percentage of Australians in favour of the referendum has dropped for the fifth month in a row.

Victoria has flipped to a majority No state since the previous survey, leaving Tasmania as the only jurisdiction where Yes voters are in the majority.

A successful referendum requires a Yes vote from more than 50 per cent of voters in four of the six states.

Lambie said Tasmanian voters were focused on cost-of-living issues.

“I’m not really hearing anything about the Voice down there, it’s all about the cost of living,” she told Sky News Australia on Monday.

“I’m not sure it will continue to hold in Tasmania … It may not … When I was down there it was all about cost of living, so that’s where we are at.”

But she also said the Albanese government had done a “lousy” job of selling the Indigenous Voice.

“People are doing it really tough out there at the moment and I can tell you, they are certainly not coming up to me talking about the Voice,” she said.

“I just think Labor has done a really lousy job of selling this, to be brutally honest.

“I think Labor has failed miserably. Once again, I hope they have a plan B ready, just in case.”

In Question Time on Monday, Dutton turned the latest polling slump on the government.

“It is clear the referendum will not deliver the moment of unity the 1967 referendum delivered,” he said.

“Will the Prime Minister withdraw his Voice referendum so we can avoid an outcome which sets back reconciliation and divides the country?”

But Albanese again stuck to his October 14 plan.

“The referendum will take place on that date and Australians will get to determine their view on that date,” he said.

“This Leader of the Opposition speaks about division when he appointed the member for Berowra as his Indigenous affairs spokesperson and shadow attorney-general – Julian Lesser (who later quit the Coalition frontbench over its No stance) … It is unfortunate the Leader of the Opposition has chosen politics over substance.”

Lambie also brushed off the Coalition’s pledge for a second referendum on constitutional recognition as a “brain fart”.

“Having a second push, you’re talking about that now but you’ve got no detail. Seriously, it’s laughable,” she said.

Nationals leader David Littleproud said Mr Albanese should split the referendum question to avoid dividing Australians, as most people backed constitutional recognition of Aboriginal and Torres Strait Islander people.

He denied a failed referendum would send a negative message to Indigenous Australians.

“The message is that Australian people have come and they’ve decided that the proposition the Prime Minister has put forward to us isn’t the proper way to unite our country or to actually close the gap,” Littleproud said in Canberra.

“Many Indigenous Australians feel that view now and that’s why I think it’s wrong for Indigenous leaders who support Yes to … make generalised statements about how Indigenous Australians will feel.”

Lambie’s criticism on Monday came as Governor-General David Hurley was expected to issue the referendum writ – the formal legal document to start the campaign in the lead-up to voting day on October 14.

The electoral roll closes seven days after writs are issued – meaning people have a week to ensure they’re enrolled.

Postal vote applications opened on Monday and close on October 11.

Hundreds of early voting centres will be available from October 2 – or, a day later in the ACT, NSW, Queensland and South Australia a day later due to a public holiday.

-with AAP