Australians have been 'conned' by 'no' campaign, says Indigenous academic Marcia Langton

Speaking at the National Press Club on Wednesday, Prof Langton said the arguments put forward by the "no" campaign were "increasingly absurd" but "effective with a growing minority".

"Australian voters have been deceived by the 'no' case and by the relentless negativity and conned into believing that the referendum proposal will not lead to better outcomes," she said.

"Where are the solutions from the 'no' case?

"They want you to accept more of the same old failure."

She pointed to a series of policy failures spanning decades, including the Northern Territory intervention in 2007, when the government sent members of the Australian Defence Force into Aboriginal communities in the Northern Territory "under the guise of protecting Aboriginal children from sexual abuse".

She said the move ignored findings of the Little Children are Sacred report.

A number of polls have shown support for a constitutionally enshrined advisory body has been on the decline in recent months.

Campaigners have just weeks left to sway voters before they head to the polls on October 14.

Prof Langton urged Australians to support the Voice proposal, saying she feared that a "no" vote would be falsely interpreted "as a mandate for governments to do nothing, and to make our lives worse".

"I think that's the greatest danger," she said.

"I also fear that a 'no' vote will be perceived, and again I say falsely, as a mandate for not establishing consultative bodies."

But Prof Langton, who co-authored the Voice co-design report, said the government needed to have a plan in case the referendum failed.

"And then I do hope that this government would turn to our report for inspiration for policy settings, to empower us, to involve us in closing the gap and other issues that affect our lives," she said.

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She said many Indigenous Australians who were on the frontlines were "very worried" about a referendum loss "because they already have little say".

"A loss will mean that they will have even less," she said.

"I do hope that the government sets out an agenda for reform that's based on common sense, on the recommendations of many inquiries and royal commissions and expert advice, before the rabble takeover and turn a 'no' vote into a mandate to cause us even further harm."

She rejected Peter Dutton's proposal for a second referendum, saying it would "serve no purpose".

The Opposition Leader has pledged to send Australians back to the polls to vote on Indigenous constitutional recognition should the October 14 referendum fail and the Coalition were re-elected.

Prof Langton joined a growing number of voices criticising Mr Dutton's watered-down proposal, which doesn't include a constitutionally enshrined Indigenous advisory body.

"I'm not interested and I know that over 80 per cent of Indigenous Australians would not be interested. And we would communicate that very clearly to the Australian people should he ever be elected," she said.

"The other matter is that it will serve no purpose. We asked for recognition through a Voice, combining the symbolic and the practical, to give us both dignity and a sense of empowerment and responsibility in matters that affect us."