Shadow attorney-general Julian Leeser quit after the party room decided to oppose a constitutionally enshrined voice to advise parliament and executive government.

Liberal shadow cabinet ministers are bound to the party position and a free vote has not been granted, but backbenchers are not tied by the same rules.

“With a referendum due later this year, I believe the time for the voice has come,” Leeser said on Tuesday.

“I believe in a national voice, drawn from local and regional bodies, and support the referendum being put this year.

“I believe the voice can help move the dial on Indigenous education, health, housing, safety and economic development.”

Leeser, who is also the coalition’s Indigenous affairs spokesman, said he was unable to reconcile his views with those of the party room after coming to the decision that constitutional change supported his liberal values.

“I believe better policy is made when the people affected by it are consulted,” he said.

Leeser added he would push the government to amend the proposed wording it had put forward in a bid to improve the chances of the referendum’s success.

“The government must seriously engage with coalition voters and it hasn’t done so to date,” Leeser said.

“This failure could ultimately put the referendum at risk. An all-or-nothing approach could deliver nothing. That’s why we must find common ground.”

But he said he would ultimately support the voice even if his amendments weren’t taken on board.

“I will fight for those amendments but ultimately I will support the referendum. I’m a supporter of the voice, it’s right that it has a place in the constitution.”

Backbench Liberal moderates Bridget Archer and Andrew Bragg, who are backing the voice, have also thrown their support behind Leeser.

“I want the referendum to be successful and I believe a ‘yes’ vote is now more likely because of Julian’s conviction,” Bragg said.

“This referendum is too important to play politics and it is not good enough to oppose the referendum on process grounds.”

Labor minister Penny Wong welcomed Leeser’s move, saying it was disappointing the opposition leader had decided to campaign against the voice.

“Julian Leeser has shown real strength today. He put his principles ahead of partisan politics and we welcome that,” she said.

But Indigenous senator Jacinta Price wants to ensure local governments are further empowered, pointing to systemic problems she says should be ironed out before a national body is considered.

The former Alice Springs deputy mayor said the voices of rural and remote Indigenous communities weren’t being listened to.

“There’s a whole lot of work that needs to be done before getting to the broader discussion. Until we do that, we can’t improve the situation on the ground,” Price told ABC Radio.

The Country Liberal Party senator, who sits in the Nationals’ party room, is staunchly opposed to a national body in the constitution, saying it would divide Australians down racial lines and add another layer of bureaucracy.

She said the disadvantage gap existed between those in rural and metropolitan areas, with Indigenous people in major cities having the same opportunity as non-Indigenous Australians.

But that was disputed by Indigenous activist and referendum working group member Professor Jack Beetson.

“If you look at the cities, you get the same socio-economic problems you get elsewhere,” Beetson said.

– AAP