Republic letter 'inappropriate': Barnett

Western Australia's premier says he refused to sign a letter calling for an Australian head of state because he did not want to suggest his views reflected those of the people in his state.

Colin Barnett said the declaration, signed by every other state and territory leader, was like a petition.

"I didn't think it was appropriate as a premier of Western Australia to take my own views and then suggest that represents Western Australia," he told reporters at an Australia Day event on Tuesday.

Mr Barnett brushed off the suggestion that his decision had anything to do with the opening of Elizabeth Quay later this week.

"We had a referendum, I supported the republic publicly during that period, but the Australian people voted and they voted against that, so I respect their decision and I don't think we should rush back into that debate," he said.

A reasonable passage of time would be 25 years, so the debate should happen again in about 10 years, the premier said.

"I've got no doubt Australia will become a republic."

Mr Barnett said the Australian flag was a separate issue but he supported the current flag.