The former Western Australian MP announced his decision to quit the party on Thursday, after Opposition Leader Peter Dutton announced the Liberals would actively campaign against the proposal which he denigrated as "the Prime Minister's Canberra voice".

"I still believe in the Liberal Party values but I don't believe in what the Liberals have become," Mr Wyatt reportedly told the West Australian.

"Aboriginal people are reaching out to be heard but the Liberals have rejected their invitation."

Mr Wyatt has been a member of the Referendum Working Group and started co-design process in the early stages of developing an Indigenous Voice to government in 2019.

The former member for Hasluck sat in Parliament between 2010 and 2022. He was the first Indigenous Australian elected to the House of Representatives, and the first to be appointed to cabinet.

As a Working Group member, Mr Wyatt stood near Prime Minister Anthony Albanese when he announced the draft wording for the referendum question and proposed constitutional amendments.

He had earlier warned the Liberals that a lack of support for the Voice could have long-term consequences for the party.

The Liberals have officially stated they will be opposing a constitutional national Indigenous advisory body to parliament, but support the concept of constitutional recognition.

The party will instead push for local and regional representatives to advocate for Indigenous people, and a legislated national Voice.

Liberal frontbencher Paul Fletcher said he would leave it to Mr Wyatt as to the reasons why he left the party, but described him as "a very distinguished Australian".

"I have enormous respect for Ken Wyatt. I think that's a respect that is felt right across the Liberal Party room," Mr Fletcher said.

"What I would say is it is very important that we have a respectful process across Australia as we go through this referendum in relation to the Voice."

The Liberal frontbench is bound to the decision to oppose the Voice proposal but the position is non-binding for backbenchers.

Mr Dutton said there were three or four members on his backbench who may advocate for a "yes" campaign.

Earlier on Thursday, Liberal backbencher Bridget Archer said she considered resigning over her party's decision to formally oppose the Voice.

"Sometimes I do consider (resigning) and then I consider the people in the Liberal Party that share my views ... people that I consider to be like-minded Liberals," Ms Archer told the ABC.

"I stay because I know that I am not the only person that thinks that way and I stay because I think the Liberal Party is at a crossroads."

Ms Archer on Wednesday told reporters that she was "disappointed" by her party's decision and would campaign for the "yes" vote on the referendum, which is expected to be held between October and December.

Mr Dutton insisted that his party would conduct a "respectful" debate and he would "not tolerate" any derogatory comments "towards Indigenous Australians or anybody who is advocating a yes position".

"I think tone is incredibly important in this debate," Mr Dutton said.

"This needs to be a respectful debate, and I treated the prime minister with respect during the course of my engagement with him, and my public commentary, and our questions in the parliament.

"And there are reasonable questions, when the Prime Minister is proposing the biggest change to the Constitution since Federation, and it is right that the questions be answered."

with Australian Associated Press