The spokesperson also confirmed there were no costings for changing a number of other flags and ensigns that are based on the current New Zealand flag -- such as the police and the Fire Service.

"Other costs, including changing flags on Government ships and on drivers' licences, will be confirmed after the referendum, but these changes will happen over time," the spokesperson said.

"The NZ Transport Agency will take a practical approach and is likely to incorporate a new flag in driver's licences at the time of individual licence renewal, after the date on which the new flag becomes the official flag."

The spokesperson said the Government would not be changing the New Zealand Coat of Arms, even though the current flag features prominently.

Mr English also revealed if there was change, it would not automatically include flags that carry the Union Jack and that he did not expect them to change.

That means the Union Jack would remain on a number of different flags and ensigns.

"The other agencies that have their own flags don't have to change anything because it's their flag, they decide what to do with it, that's not what's being voted on," Mr English said.

"Where the armed forces have their own flags, they keep their own flags, that's up to them to decide what to do. I assume they'll just keep their flags because the public's not voting to change the armed forces flag, we're voting on the New Zealand flag."