Prince and PM may chat about weather

A prince in line to become Australia's head of state is about to meet a republican prime minister who'd rather he didn't.

Chances are the elephant in the room - republicanism - won't cast too big a shadow over the royal tour.

The prince and the politician may well turn to chatting about the weather when they meet on Wednesday.

That's because Prince Charles and Malcolm Turnbull share deep concerns about the long-term forecast - namely climate change and the need to reduce carbon emissions.

They may revisit that conversation when they attend the Commonwealth leaders' meeting in Malta later this month, then the Paris climate change conference in early December.

Mr Turnbull was the leader of the failed campaign for Australia to become a republic in 1999 but he remains committed to eventually ditching the monarch as head of state.

In a pointed reversal, Mr Turnbull recently overturned Tony Abbott's "captain's call" to restore knighthoods and damehoods to the Australian honours system.

In Mr Turnbull's 1993 book The Reluctant Republic he describes the marriage of Charles and Diana as "a miserable pretence" and notes that the Prince of Wales maintained a sexual liaison with Camilla Parker Bowles throughout.

Mr Turnbull wrote that it was difficult to believe that Prince Charles could ever be accepted as king.

But on news last month that Charles and Camilla were to visit Australia, the prime minister set himself up to be the charming host.

"Lucy and I will be delighted to welcome the prince and duchess and expect Australians will be eager to display our country's hospitality to the royal couple," he said.

Mr Turnbull made it clear soon after becoming prime minister that any move to a republic would only occur when the Queen's reign ends, saying he was more concerned about the economy than a change of Australia's head of state.

"The republic issues cannot belong to a politician, it's got to be a genuine popular movement," he said.

"My own view for what it is worth is that the next occasion for the republic referendum to come up is going to be after the end of the Queen's reign."

When asked about Charles' take on the republican debate, a spokeswoman at his Clarence House residence in London referred AAP to a speech he made in Sydney on Australia Day in 1994.

In that address he said there were those who wished to see a change in Australia's institutions.

"And perhaps they are right ... some people will doubtless prefer the stability of a system that has been reasonably well tried and tested over the years, while others will see real advantages in doing things differently.

"This is something which only you the Australian people can decide," Charles stressed.

"Whatever course you ultimately decide upon, I can only say that I will always have an enormous affection for this country."