Bill Shorten says the prime minister has put an Australian republic in the too-hard basket after Malcolm Turnbull restated his belief the change wouldn't happen until after the Queen's reign.

Speaking at the 25th anniversary of the Australian Republic Movement he helped found, Mr Turnbull advocated a "grassroots" approach to reviving a push for a referendum and said an initial advisory vote should be held to determine the form a republic would take.

Any move had to be genuinely popular, otherwise the lessons from the failed 1999 referendum hadn't been learned.

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Mr Shorten reiterated his support to work towards a referendum, tweeting: "Let's work together to deliver an Australian head of state."

But the Labor leader also took aim at Mr Turnbull's comments about waiting until after the Queen's reign.

"Climate change, marriage equality, housing affordability, now republic too hard for Turnbull," he wrote.

"Time for the PM to lead his party, not follow."

Mr Turnbull said those advocating for a republic had to acknowledge the issue wasn't keeping Australians awake at night.

And just because passions had been stirred by Tony Abbott's widely panned decision to award Prince Philip a knighthood, no one should delude themselves that was a game-changer.

He urged the Australian Republic Movement to mobilise a substantial majority of people and politicians pushing for the change.

My offer still stands - let's work together to deliver an Australian head of state. — Bill Shorten (@billshortenmp) December 17, 2016

The Australian Monarchist League criticised Mr Turnbull for attempting to pacify monarchists while giving hope to republicans - and failing to do either.

"The ultimate result of the prime minister's speech is that not only will the Liberal Party further haemorrhage members to minor conservative parties but it will also lose ardent republicans," national chair Philip Benwell said.

Senior minister Mathias Cormann said he was well-known as a constitutional monarchist and nothing the prime minister said had changed that.

"I heard the prime minister say that the issue was settled at the referendum a little while ago - I certainly agree with him on that," he told Sky News on Sunday.

One Nation senator Malcolm Roberts said the prime minister should focus on the Australian economy and jobs, not "distractions".