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Key said today he would prefer to continue working with Act, the Maori Party and United Future following this year's election but could add Colin Craig's Conservative Party.
In a statement ahead of his post Cabinet press conference this afternoon Mr Key said while there had been differences between National and its current three partners, "together our four parties have formed a stable and successful Government since late 2008".
"We also have policy differences with the Conservative Party, however it is likely that there would be enough common ground to work with them in Government."
Mr Key ruled out working with Labour, the Greens and Mana, "on the basis that there is insufficient common ground to achieve a stable and successful working relationship".
"These parties represent a far left wing agenda that we do not believe is good for New Zealand," Key said.
Key said a post-election working relationship was very unlikely with Winston Peters' NZ First but would not rule the possibility out ahead of the election.
"In 2008 we ruled them out because we were unable to reconcile some of their statements on the Glenn donation matter. Six years has passed and, should New Zealand First be returned to Parliament, we would not rule out a discussion after the election."
Key said he was now refusing to rule out working with Mr Peters because a few things had changed in recent years.
That included the fact that it was now six years since the Owen Glenn donations saga.
Since then Peters and NZ First had been returned to Parliament and if he was returned again this year that would indicate he had passed a test with the public.
Another factor was that there were some National voters who would rather see a National Government with NZ First than a Labour Greens Government.
Key said one unlikely option was that National could form a Government with NZ First abstaining on confidence and supply.
Key said it was most likely that any post-election working relationships would be via Confidence and Supply Agreements, "as these have worked well in the past two Parliamentary terms".
Labour leader David Cunliffe said Key's announcement on potential partners was "the dance of the desperate all over again''.
Key's comments on NZ First were "very interesting '' given he ruled him out six years ago saying it was a matter of principle not policy.
"Clearly his principles have a half-life of less than six years, perhaps they're a McDonald's special for a limited time.''
Cunliffe said Labour could work with any other party other than National, Act or the Conservatives, although talks with Dunne were very unlikely.