Bill Shorten has promised to hold a vote on Australia becoming a republic if Labor wins the election.
In its budget costing plan released on Friday, the Australian Labor Party has put aside $55 million to stage a public vote on the issue in 2021-22.
It plans to first hold a national plebiscite to gauge the level of public support to replace the Queen as head of state with an Australian.
If that vote achieves enough support, a referendum would then need to be held to change the Constitution.
In a referendum, the change is only passed if it wins the support of the majority of voters and more than half of states and territories.
In 1999, a public vote on the issue failed with 55 per cent of Australians voting to keep the British monarch as head of state.
In a bitter campaign, many republicans voted against the move as they wanted the new head of state to be directly elected - similar to the Irish model - instead of one appointed by parliament as was proposed.
The Queen, who has recently turned 93, last visited Australia in 2011.
In an opinion piece written for The Age website in 2015, Mr Shorten laid out his commitment to holding a vote on Australia becoming a republic if elected to power.
He said: “We should go to our region and the world proudly independent – declaring that we are no longer going to borrow a monarch from another country on the other side of the world.
“Our constitution came into being as an act of the British parliament – 114 years later, our nation has changed, our place in the world has changed, and our constitution should change with it.
“The republic debate is a chance for all of us to bring our constitution home, to vote our national birth certificate into existence as an Australian document, for our times.”
The Liberal/National coalition has no plans to change the current constitutional arrangements.