The National Party still leads Labour by 18 points in the latest One News Colmar Brunton opinion poll.
National's popularity has dropped by one point, but Labour has not moved in the past week.
The poll of 1000 people puts National at 51% and Labour on 33%.
National's loss may been the Greens' gain, with that party moving up by 1% from last week to 8%.
No other minor party reached the 5% threshold on party votes.
The poll has a margin of error of plus or minus 3.1%.
Radio New Zealand's political editor says the result is in stark contrast to two other polls issued on Friday which suggested the gap between the two major parties was narrowing substantially.
The Roy Morgan poll released on Friday had National on 40.5% and Labour on 37.5. A TV3 poll that night had National on 45% and Labour on 39%.
But Sunday night's poll showed no change from the huge lead National has enjoyed for much of last year.
Radio New Zealand's political editor says there are huge differences in these poll results.