The prime minister has praised former Indigenous Australians minister Ken Wyatt as taking a principled stand in quitting the Liberal Party over its position on the voice to parliament.
His comments come as one senior member of the coalition's shadow cabinet indicates he is unlikely to actively campaign for the 'no' side in the upcoming referendum, putting him at odds with his party leader.
Prime Minister Anthony Albanese on Friday said Mr Wyatt had "shown a great deal of principle" in resigning his Liberal membership after Opposition Leader Peter Dutton revealed the party would not support enshrining the voice in the constitution.
"(Mr Wyatt) worked very hard for such a long period of time ... for years (former prime minister) John Howard said we needed to recognise Aboriginal people in our constitution and it hasn't happened," Mr Albanese told Sydney radio station 2GB.
"Peter Dutton has underestimated how many Liberal-National Party voters will vote 'yes'."
Mr Wyatt, the first Indigenous person to be elected to the House of Representatives, resigned from the Liberals on Thursday, saying he did not believe in what the party had become.
He had called for the party to allow a conscience vote as he expected many MPs would back the 'yes' campaign in the Indigenous voice referendum if given a chance.
The Guardian reported on Friday that three leading Liberal moderates - Simon Birmingham, Paul Fletcher and Marise Payne - spoke out in a shadow cabinet meeting on Wednesday against the party's plan to oppose the voice.
The trio reportedly argued in favour of a free say for all MPs but were voted down and will be bound to the party's position as members of the shadow cabinet.
Mr Dutton has said he will campaign for the 'no' side, dismissing Labor's plan for a "Canberra voice" that will not deliver practical benefits for Indigenous Australians.
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.
Senator Birmingham refused to say on Friday whether he would actively campaign against the voice.
He said his approach would be "one of respecting the Australian people as they go about making their decision".
He added 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.
