Prime Minister Bill English has revealed he voted for the flag change, but says John Key's failed referendum on this issue showed the perils of politicians rather than people trying to drive change.
It is the first time English has revealed how he voted in the flag referendums. He had refused to give his view at the time because he was in charge of the referendum process.
Now he is Prime Minister, English said the flag referendum showed constitutional changes such as the flag or a move toward a republic should not be led by politicians.
"That is the lesson from the flag referendum. I oversaw the process for changing the flag, I voted for changing the flag. In the end, a lot of the voting became a bit of a political vehicle, probably because it was proposed by the Prime Minister.
"So I think in future that constitutional change needs to come from the will of the people."
He said that would apply to any move to become a republic as well.
English was speaking to the Herald in London, where he also discussed his views on republicanism.
English said he did not New Zealand to become a republic even after the reign of Queen Elizabeth. That is the time when many believe the issue will be debated in countries such as New Zealand and Australia.
He believed that "people would generally support the monarchy and its continuation."
Although English missed out on meeting the Queen on this trip because of her recent illness, he said he had met her in the past and hoped to do so again in his role of Prime Minister. She had also sent a Christmas card to him after he became PM.
He said the monarchy was a "practical arrangement" that had worked for New Zealand and there was high respect for the Queen.
He also believed the upheavals of the Brexit vote would be good for the monarchy. "I think it does [help]. Part of the strength of it has been it is a point of stability in changing times and that is particularly obvious now."
He said he was a monarchist.
"I support the monarchy. I've looked at the arguments for a republic, but I think in the long run it's important that important constitutional change comes from the people - so bottom up rather than top down.
English has previously said he was a monarchist - although he has joked that it would be difficult to be as enthusiastic about it as Key was. Key had visited Balmoral and had several meetings with the Queen, including once promising to advocate for her in the Commonwealth for changes to the rules of succession to allow daughters to be treated the same as male heirs.