Changing the New Zealand flag will bring with it a cost of up to $458 million to change passports, according to New Zealand First.

On Thursday, Newshub revealed the Government had no idea what the cost to taxpayers would be to roll out a flag change if the alternative option wins the referendum.

New Zealand First leader Winston Peters says he has since done some further investigating.

"We asked the Minister of Internal Affairs what would the cost be if every valid New Zealand passport had to be recalled and re-issued," says Mr Peters.

"The minister replied 'from $0 to $458,221,788'. So, the cost of changing the passports would be $458 million, but by saying $0 suggests no reissue is contemplated by the Government.

"If the alternative flag was adopted we would have the bizarre situation of having our passports with one flag, and our country with another flag."

The only place on the passport where the flag is visible is in the coat of arms. A spokesperson for Finance Minister Bill English told Newshub there are no plans to change the coat of arms or passports even if the flag is changed.

New Zealand First has raised several concerns about the flag referendums, from alleging inaccuracies in the translation on voting papers to expressing anger that immigrants were allowed to vote.

"This is just another example of the Government's incompetence and the work they never did when they put the issue to the New Zealand public," says Mr Peters.

"This week the Prime Minister said he was unconcerned that there had been no work done to find out the full cost of a flag change."

Last month a Newshub/Reid Research poll found only 30 percent of New Zealanders wanted to change to the Kyle Lockwood silver fern flag – the design Prime Minister John Key has been trying to rally support for.

"The attempt to change the flag has been a shambles from the start and it's appalling that it is costing the country $26 million," says Mr Peters.

The second binding referendum on the New Zealand flag has voters deciding between the existing flag and the Lockwood design and closes on March 24.

Newshub.