The Maori Party could hold the balance of power with National's support slipping, according to a new political poll.
The 3 News/Reid Research poll has National at 45.8 per cent support, down 4.0 per cent from its last poll.
Labour was at 33.2 per cent, up 3.8 per cent, with the Greens the only other party above the 5 per cent threshold at 14.4 per cent, up 0.3 per cent.
NZ First was on 2.8 per cent, the Maori Party on 1.4 per cent, the Conservatives on 1.1 per cent, ACT on 0.5 per cent support and Mana on 0.3 per cent. No figure was given for United Future.
Assuming the minor parties retained their current electorate seats, National would hold need all its current partners to support it to get to the 62 seats it needs to stay in power.
National would have 57 seats, ACT one, United Future one and the Maori Party three seats. On the left, Labour would have 42, the Greens 18 and Mana one.
If the Maori Party chose to support a Labour-Green alliance, the left could form a government.
Two other recent polls, a Roy Morgan poll before the May 24 budget and a One News poll after it, also showed National at similar levels of support.
The preferred prime minister rankings had National leader John Key at 40.5 per cent, Labour leader David Shearer at 12.3 per cent, NZ First leader Winston Peters at 4.8 per cent and Green co-leader Russel Norman at 4.0 per cent.
The poll of 1000 voters was taken from May 29 to June 6 and has a margin of error of plus or minus 3.1 per cent.