The Royal New Zealand RSA has labelled the timing of the referendum that could lead to a new flag as unacceptable.
National president BJ Clark said just as New Zealand approached the Anzac centenary, it was being undermined by the establishment of a committee to decide whether the present flag should be cast out, at an "excessive" cost of $26 million.
"A hundred years ago our forces served and sacrificed under the same flag that flies today. It is inappropriate that this debate occurs as we commemorate the centenary of the First World War," Mr Clark said.
"For many who've served, our current flag is symbolic of the sacred oath they made to protect the peace and security of New Zealand. Our men and women have made terrible personal sacrifices, and we honour their courage and commitment every time the current New Zealand flag is flown."
The RSA believed that the current New Zealand flag was just as relevant now as it was when the first Anzacs landed on the shores of Gallipoli.