Prime Minister John Key is holding out hope of a change of national flag, despite strong support for the status quo.

Labour l eader Andrew Little says the flag issue can be addressed again when New Zealand considers becoming a republic.

Voting on the second flag referendum is now at the halfway point.

Mr Key, who has voted for an alternative flag, said yesterday he remained optimistic that the flag would change.

Advertisement

"I hang around in the wrong circles obviously because the wrong people keep telling me they've all voted for change," he told reporters.

"There must be a lot of people voting for change the other way because the polls tell you that. "

Mr Key also addressed criticism of the referendum's cost. He highlighted reports in Australia that a referendum on same-sex marriage there would cost A$520 million ($585 million).

"When people say $ 26 million is a lot - it is an awful lot of money and I appreciate that - but I think that it's a debate that's been worth having."

Mr Little said he had voted to retain the existing flag.

"I don't think the new flag that has been put up at all represents New Zealand," he said.