Nationals MP Andrew Gee has announced his resignation from the party and will sit in federal parliament as an independent.
Mr Gee, who represents the NSW seat of Calare, said he was leaving the junior coalition party after its decision to oppose the Indigenous voice to parliament.
"I can't reconcile the fact that every Australian will get a free vote on the vitally important issue of the voice, yet National Party MPs are expected to fall into line behind a party position that I fundamentally disagree with and vote accordingly in parliament," he said in a statement.
"While I respect the views of my colleagues, this just isn't right. I didn't bring on the debate within the Nationals over the voice or the press conference that followed."
Mr Gee said recent flooding in NSW that devastated rural areas had "brought home" the importance of speaking up.
"Now more than ever the communities of our region need their MP in their corner advocating for that support, no matter the political stripe of the state or federal government," he said.
"While I accept that in politics compromises have to be made, there comes a point where not speaking out freely can compromise the interests of those we represent."
Nationals Leader David Littleproud said he was disappointed by Mr Gee's decision, but he had accepted his "unfortunate" departure.
"While the federal Nationals remain united in our decision to oppose the voice to parliament, I have stated from the beginning that one of the great things about our Party Room is the ability to have different opinions and speak and vote freely on issues that matter to individual members and nothing has changed," Mr Littleproud said.
"We will continue to work hard for western New South Wales and find a candidate who will best represent them at the next federal election."
Prime Minister Anthony Albanese said he respected Mr Gee's decision and would work alongside the new crossbencher to promote the Yes vote for the voice.
"Andrew Gee has made a principled statement about his commitment to constitutional recognition for Aboriginal and Torres Strait Islander peoples, but also for a constitutionally recognised voice to parliament," he told reporters in Sydney.
"I'm pleased that Andrew Gee will be campaigning for a Yes vote. But I say to members of parliament as well: don't miss the opportunity to be a part of enriching our nation and making us even stronger in the future."
The junior coalition partner described the voice to parliament, which is set to go to a referendum in the second half of 2023, as divisive, and the body would do little to improve the lives of Indigenous people.
Mr Gee broke ranks with the Nationals following the party's announcement of its opposition to the voice, calling it "absurd" for him to be expected to change his stance on the issue.
The federal MP said the decision had been difficult, but he would be now able to serve his electorate "free from party constraints".
"I wish David Littleproud as leader of the Nationals well. He's a good man and he has my respect. This issue unfortunately runs deeper than the role of just one person," he said.
"I will continue the vitally important work of securing the bright future of our region."
Mr Gee was elected to the seat in 2016, after previously serving in NSW parliament.
Mr Albanese said the voice to parliament would be an opportunity to unite the country.
"This should not be an issue of partisanship. And that's why we have very deliberately reached out, just as First Nations people have reached out as well," he said.
"This is not a government proposition, this is a proposition from the Australian people, a gracious offer which should be accepted."
