Announcing the date this afternoon, Mr English said National will take nothing for granted in its campaign and that the economy was always the central election issue.
The PM was not ruling out working with NZ First after the 2017 election, but said it was "unlikely".
He said his preference was to continue working with current partners - Act, United Future and the Māori Party.
"Together our parties have provided a stable and successful government at a time of great uncertainty in many parts of the world," said Mr English.
