Former prime minister Malcolm Turnbull says the republican movement needs to "thrash out" a model for Australia to break away from the monarchy before pushing for another referendum.
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Mr Turnbull said the question of whether a future Australian head of state would be directly elected by the people or appointed by parliament should go to a plebiscite.
Once that had been decided, the question of whether Australia should become a republic could go to a referendum.
"I've had 20 years to think about it, I tell you, it's my considered opinion ... that we cannot afford to have another referendum where we are fighting on two fronts," Mr Turnbull said.
"What we need to have is a plebiscite, a public vote which sets out a direct election model and a parliamentary appointment model.
"We need to thrash that out for months ... have a good old barney and come to a decision."
Mr Turnbull was speaking at a dinner marking 20 years since the failed republic referendum in Canberra on Tuesday night.
Mr Turnbull, who led the "yes" campaign, said the referendum failed because of internal divisions within the republican movement over how the head of state would be appointed.
"What happened in 1999 was we had two debates going on at the same time," Mr Turnbull said.
While former Labor prime minister Paul Keating also suggested a republic plebiscite, he believed the Australian public would trust parliament to come up with the model.
"He's an idealist. I honestly think a plebiscite where you just said 'do you want to be a republic' would get a thrashing," Mr Turnbull said.
"People would say you're asking for a blank cheque sort of republic. So I would sincerely counsel any future prime minister not to undertake that but I think we've got to deal with direct election versus parliamentary appointment first."
And with Brexit approaching, the question about Australia's future as a constitutional monarchy was all the more pressing, Mr Turnbull said.
"What happens when the United Kingdom ceases to exist? What happens if Scotland decides to secede and there is no longer a United Kingdom?" he said.
"You can see the absurdity and indignity of having our constitution depend on decisions and events over which we have no control at the other end of the world."
Labor leader Anthony Albanese joked that after the trainwreck Prince Andrew interview, the hard work had been done for the republican movement.
"Congratulations everyone, we'll become a republic next year," Mr Albanese said.