The 3 News-Reid Research poll put support for National on 54.4 per cent, up 4.4 percentage points, while support for Labour dipped two points to 32.6 per cent.
That means National would have enough votes to govern alone if the poll results were reflected in an election.
The resurgence comes after the last 3 News poll showed Labour and its support parties would have enough support to form a government.
The new poll shows support for the Greens has fallen by 2.2 points to 10.8 per cent, while support for New Zealand First has increased by 1.4 points to 3.4 per cent - which is still below the 5 per cent threshold needed to get back into Parliament under MMP.
Of the minor parties, the Conservatives picked up 0.2 of a point, putting them on 0.9 per cent, while the Maori Party dropped 0.8 to 0.4 per cent.
Act and Mana dropped 0.1 each, to 0.1 and 0.0 per cent respectively.
Mr Key remains the preferred prime minister, with 41.0 per cent support.
Support for Labour leader s David Shearer was at 10.0 per cent, New Zealand First's Winston Peters at 4.7 per cent and the Greens co-leader Russel Norman at 1.8 per cent.