Wellington: New Zealand's acting prime minister has added fuel to a trans-Tasman war of words by claiming Australia copied the Kiwi flag and should get a new one.

During New Zealand's failed 2016 referendum into replacing its flag, confusion between the Australian and Kiwi ensigns was often raised by those looking for change.

Asked about the matter this week, New Zealand Acting Prime Minister Winston Peters - whose party fiercely opposed a change - blamed Australia.