Support for the National Party has fallen in the latest One News Colmar Brunton Poll, while the Green Party's popularity has jumped.
National gained 46% support in the poll compared with 49% in the previous poll in May.
The Labour Party's support held steady at 33% but the Green Party's support rose from 9% to 14%.
Based on this poll neither National nor a Labour-Green coalition could govern without support from other parties, most likely New Zealand First.
Radio New Zealand's political editor reports that while it only got 3% support in this poll New Zealand First is likely to get over 5% next year, as it did in the last election.
The Maori Party, Mana, ACT and United Future could also have an influence if they hold on to their electorate seats.
Labour leader David Shearer says the Government's handling of the controversy around the country's electronic spy agency has hurt National's support.
"The fact that both the GCSB legislation is going through at exactly the same time as the debacle around the emails and phone records of journalists being looked at is giving people I believe a real concern that the Government is not on top of things."
The poll surveyed 1000 voters and has a margin of error of plus or minus 3.1%.