'Yes' campaigners have blamed misinformation and a lack of detail for the defeat of the referendum to enshrine an Indigenous voice in the constitution.
As counting continued on Saturday night, the first referendum since 1999 was on track for defeat with a progressive national 'no' vote of more than 56 per cent.
'Yes' campaign leader Dean Parkin told a Sydney function those in favour of the change had done all they could to get it over the line.
"We did all we could to alleviate those doubts, we did all we could to ensure that the proposal was strong," Mr Parkin said, in a televised address.
"But it is clear from the result that we were not able to reach you through that.
"And we were not able to reach you and come through what has been the single largest misinformation campaign that this country has ever seen."
Liberal senator Andrew Bragg, who campaigned for the 'yes' case despite his party being against it, said the government had made three fateful decisions.
The first was refusing to set up a long-running parliamentary inquiry into constitutional reform models.
The second was not publishing draft legislation setting out the structure of the voice and its functions.
And the third was the "failure to compromise".
"I feel for the Australians who believe in a grassroots structure for giving advice to the government on special laws and policies for Indigenous people," Senator Bragg said in a statement.
"This has always been a good and fair idea. We should always listen to the grassroots."
Labor frontbencher Malarndirri McCarthy said it was important to respect the result, but there would be a mix of feelings.
"I do think it will take time but one of the things I do know about our mob certainly is we've had many disappointments over decades, and centuries really," she told the ABC.
"And I think we are resilient people and we just will take stock."
Beyond Blue chair Julia Gillard and director Ken Wyatt said the result would be distressing for many Indigenous people, but services were available to help them.
"For First Nations peoples, the research clearly shows that social and emotional wellbeing is strengthened when self-determination is at the heart of decision-making," they said in a joint statement.
"That's why we supported the voice and believe a First Nations community-led approach to mental health will lead to better outcomes. We still believe Australians want a just and compassionate country."
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