A poll suggests 43% of people support New Zealand becoming a republic.
The telephone survey of just over 1000 voters was commissioned by the Republican Movement of Aotearoa.
The group claims the level of support for a republic has roughly doubled over the past 20 years and the debate should be revisited.
But the Monarchist League of New Zealand says the timing of the poll is crass, coinciding with the Queen's 83rd birthday, and the movement is clutching straws.
Its says telephone polls are unreliable and it believes support for the monarchy has remained steady since the late 1980s at about 60%.