A new political poll suggests Labour could lead a three-party coalition into government.

The Roy Morgan poll released on Friday showed the governing National Party still on top, but its support had gone down 2.5 percent from the last poll in late April to 44.5 per cent.

Labour was up 1.5 per cent to 30 per cent while the Greens were unchanged at 15 percent, putting their combined support level at 45 percent.

This would mean New Zealand First, up 0.5 percent to 5.5 per cent, could decide which party led the government.

National leader John Key has repeatedly said he wouldn't work with NZ First leader Winston Peters, though Mr Peters campaigned at the last election on sitting on the cross-benches and there are question marks over the relationship between NZ First and the Greens.

Hone Harawira's Mana registered 0.5 percent, unchanged from the previous poll.

ACT, whose leader John Banks has been mired in controversy over donations made during his unsuccessful Auckland Mayoralty campaign in 2010, is at zero percent support, down 0.5 per cent.

"The continuing scandals involving John Banks appear to not only be effecting the ACT NZ vote but also rubbing off on the Key government," Roy Morgan spokesman Gary Morgan said.

United Future is up 0.5 percent to 1 percent, while the Maori Party is down 0.5 percent to 1 percent.

Other unnamed parties on the Roy Morgan website secured 2.5 percent.

The poll also found 51 per ent of New Zealanders thought the country was heading in the right direction, down 4 percent, with 35.5 percent saying it was going in the wrong direction, up 3 percent.