Shadow Attorney-General Mark Dreyfus said it's disappointing the Prime Minister is not moving faster towards Australia becoming a republic.
Malcolm Turnbull met the Queen at Buckingham Palace before leaving London to return to Australia.
The former Republican leader hailed Queen Elizabeth for her steady, dignified public service - while observing protocols not to divulge what was discussed.
But he made clear there won't be a move for Australia to become a Republic while the current monarch is on the throne.
Mark Dreyfus has told Sky News it's time the Prime Minister took action on a republic.
'There was a massive disappointment in 1999 when the referendum failed. Malcolm Turnbull of course was the man who said that John Howard had broken the nation's heart with the failure of that referendum,' he said.
'It's disappointing that Malcolm Turnbull as Prime Minister isn't taking more active steps towards putting Australian on the path again to a republic, which is supported by a majority of Australians.'
Speaking to reporters before the final official event for Mr Turnbull before heading back to Australia, Mr Turnbull, who co-founded the Australian Republican Movement, said politics is 'full of unpredictable events'.
'Even republicans like myself can be, and in my case are, very strong Elizabethans,' he said.
However, Mr Dreyfus said Queen Elizabeth would be the perfect monarch to handle the matter.
'I differ from the prime minister on thinking it has to await the end of the reign of Queen Elizabeth, I think in fact she would be the perfect person with grace and dignity to deliver a republican Australia.
'It's something she's done for many countries in the commonwealth'.
Malcolm Turnbull paid tribute to the 91-year-old monarch as having embodied 'selfless public service, dignity, wisdom and leadership for longer and more magnificently than anyone alive today'.
The monarch has been invited to open the Commonwealth Games on the Gold Coast in 2018.
Asked whether he expected confirmation of which royal might attend, Mr Turnbull said: 'I may be better informed this afternoon.'
Mr Turnbull has publicly advocated for a republic, but believes such a change would not be supported by Australians during the Queen's reign.
ARM is pressing for a national vote in 2020 on whether people want an Australian head of state and how one should be chosen.
This would be followed by a full referendum in 2022 to change the constitution.
Mr Turnbull said in a speech in December his preferred model was an advisory plebiscite offering a choice between two republican models - most likely direct election and parliamentary appointment.
Once the model is chosen at the plebiscite, the parliament would formulate the terms of the amendment in line with the people's choice and present it at a referendum.
ARM called on the prime minister to make clear to the Queen Australia would still be a commonwealth country if Australians vote to become a republic.