National Party leadership will be discussed "in the next few weeks", Bill English says.

Speaking 90 minutes after New Zealand First leader Winston Peters announced his party would go with Labour in a coalition, English promised National would be "by far the strongest Opposition party that Parliament has seen, because almost one in two New Zealanders did support us. For a party going into Opposition, we're in better shape ... with talent and energy and ideas.

"A group of people we've geared up to be a government. We're not going to be ... we accept that."

English said he did not know why Peters had chosen Labour over National, but the negotiations, from his point of view, had been "satisfactory".

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He described it as an "unusual" result for MMP. He questioned whether there was a result anywhere in the world where a party took 44 per cent of the vote and did not win. But he accepted the result. He added: "The result is clear. We accept that result."

He did say, though, that speculation about Cabinet posts being a sticking point was "quite wrong".

"Tonight is the opportunity to thank all the people who engaged with us, supported us ... but also to say the Government is going to change ... we wish them well."

His leadership of the party would be discussed in the next few weeks.

English said the way he found out about the decision was a "detail".

Asked about the dollar's fall yesterday, English, who was Finance Minister in John Key's Government, said: "The economy is in pretty good shape, actually ... since the GFC. That presents a very good opportunity for an incoming Government, and I hope they take it."

He called Jacinda Ardern's rise a "remarkable performance" and said his advice to her was to take the role very seriously but not take herself too seriously. English said she should build on the positive direction the country had been going in.