Prime Minister Anthony Albanese says he is disappointed federal Liberals rejected the government's proposal to enshrine a voice in the constitution as he had hoped the idea would transcend politics.
"It's a clear request from Indigenous Australians. It's a gracious hand to have, to walk on that path of reconciliation," he told Sydney radio station 2GB on Friday.
But Mr Albanese added he was still optimistic the referendum would pass.
"(Opposition Leader) Peter Dutton has underestimated how many Liberal-National Party voters will vote 'yes'," he said.
The Liberal Party will support constitutional recognition for Indigenous people but has rejected enshrining a national voice, instead calling for legislated regional and local voices to be established.
Mr Dutton said the prime minister wasn't properly informing people about the consequences of putting the voice in the constitution.
"That's for political reasons, because he knows that if he explains it, people will fall away," he said.
Mr Dutton added that polls pointing to the referendum just passing were "soft".
"The numbers at the moment are inflated because people have a general inclination that they want to support a better outcome, but once they understand what it is the prime minister is proposing ... the numbers start to fade away," he said.
Deputy Liberal leader Sussan Ley said the prime minister issued an edict not an invitation to work together.
"We are asking questions, it's not good enough for the prime minister to issue demands that people follow his lead," she said.
Referendum working group member Marcia Langton earlier attacked the opposition leader for suggesting the proposal was for a "Canberra voice" that would be stacked with academics and not represent the views of Indigenous people around Australia.
"His opposition to the voice relies absolutely on deceit and misrepresentations and, I have to say, a great deal of ignorance," she said.
Cabinet minister Jason Clare also hit back at the Liberals for accusing the government of not putting out enough detail about the voice.
He said while the prospect of the referendum passing had become harder, he still had faith Australians would vote 'yes'.
"The Australian people are bigger and better than the mean and negative Liberal Party," he said.
"I have faith they will meet this moment later this year."
Tasmanian Liberal moderate Bridget Archer said she was not the only member who felt their party was at a crucial juncture and she pledged to campaign in support of the voice despite her party's position.
Ken Wyatt, the first Aboriginal person to hold the Indigenous Australians portfolio, has resigned from the Liberals, saying he did not believe in what the party had become.
Liberal frontbencher Simon Birmingham, who is bound to the party position as a member of the shadow cabinet, refused to say whether he would actively campaign against the voice.
The senior moderate said his approach would be "one of respecting the Australian people as they go about making their decision".
Senator Birmingham said former Liberal treasurer Peter Costello campaigned for a republic while then prime minister John Howard campaigned against it and a similar split could be replicated with the voice.
Victorian Premier Daniel Andrews said governments needed to make a better effort at listening to the voices of Indigenous people.
"We are big enough in this country, we are generous enough, we're smart enough to take this step forward," he said.
"For far too long, we've told Aboriginal people how it's going to be and that has to stop."
