The Returned and Services Association says it cannot afford to wait until after the centenary of Anzac Day this month to take its fight against proposed changes to the country's flag.
The New Zealand Flag Referendums Bill was introduced to Parliament last month and the closing date for submissions on proposals to the justice and electoral committee is Thursday, April 23.
RSA chief executive David Moger said the timing of the flag debate was insensitive.
"We feel it's inappropriate that these submissions close two days before April 25 when we will all be standing there as dawn breaks under the New Zealand Flag," said Mr Moger.
"We would prefer to allow the centenary to be commemorated without distraction but we have been forced to take action now because of the submissions date."
Mr Moger said the RSA would fervently express its case to the committee but it also called for people to either make submissions to the committee or to write to their MPs expressing support for the existing flag and opposing the need for a $26 million double referendum.
Advice on how to prepare and submit a letter or email to an MP is on the RSA website.
The committee has to report back to Parliament by July 19.
Mr Moger said the RSA's submission would ask why the Government was seeking change.
The other plea would be that if there had to be any referendum then it should be one seeking a simple yes or no to the existing flag.
Last month, a committee met to choose the design of four alternative flags from which one would be selected in the first referendum.
This design would be pitted against the existing flag in a second referendum.
Mr Moger said hundreds of New Zealanders had contacted RSA branches around the country saying they did not want a new flag and did not understand why the debate was being afforded such priority.
"We are getting a lot of support from young people who ask 'what's the point?' and say they are happy with the flag."
Flag Referendums Bill
• Sets the process for two referendums on the flag.
• Bill to be considered by Parliament's Justice & Electoral Committee.
• Submissions close Thursday April 23.
• Select committee to report by July 19.
• First referendum: voters rank preferences from a shortlist of four designs.
• Second referendum, next year: voters choose between the old and new flags.
• $26 million cost of holding referendums and 12-person design panel.