National's leader is calling Winston Petersâ bluff on bottom lines, saying heâ ll flip flop on demands if heâ s needed to help form a government.

The New Zealand First leader says his partyâ s unique, in that it wonâ t sell out on Kiwisâ interests.

But John Key believes that may change, if Mr Peters canâ t get his deal breaker policies, like a Royal Commission on Dirty Politics over the line, with a major party.

"It's just not practically possible for parties to say they have an absolute bottom line. In principle it might be a nice idea but if you are so resolute on sticking to that then ultimately you have to have another election."