National will keep candidates in Epsom and Ohariu, despite asking voters to opt for David Seymour and Peter Dunne.

Prime Minister Bill English has called for National voters to back ACT leader David Seymour in Epsom and United Future leader Peter Dunne in Ohariu.

He said National intended to work with those two support parties in the September 23 election - but did not include the Maori Party in that comment.

However he did note that In February, he made it clear that if National was re-elected his preference was to continue working with ACT, the Maori Party and United Future.

Prime Minister Bill English has called for National voters to act tactically in Ohariu and Epsom.

"While we don't always agree, our four parties have maintained a stable and successful Government since late 2008 and we would like to see that continue for the benefit of New Zealanders," English said.

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"We are encouraging National supporters to give their electorate vote to ACT candidate, David Seymour, in Epsom, and United Future candidate, Peter Dunne, in Ohariu – and their party vote to National.

"To be clear, we want to increase our party votes in those electorates and that's what our National Party candidates will be working hard to do."

English said if he was in the Ohariu electorate he would vote for Dunne - a different stance from that of former leader John Key who said in 2014 he would vote for the National candidate in Epsom even though he signalled other National supporters should back Seymour.

He said his candidates Brett Hudson in Ohariu and Paul Goldsmith in Epsom would be "working hard" knocking on doors and asking voters not to vote for them but for the other party's candidate.

DAVID UNWIN/STUFF National is calling for its supporters in the Auckland seat of Epsom to vote for ACT leader David Seymour.

"That's basically the message, yes."

But he did not think it was necessary to pull the National candidates from the ballot.

National would rather work with its three existing support parties than with NZ First, but it would work with whatever cards the voters dealt.

MONIQUE FORD/STUFF Longtime Ohariu MP Associate Health Minister Peter Dunne.

NZ First leader Winston Peters had "history in Government, which is colourful".

He said National would be encouraging voters on the Maori role to vote for both the Maori Party and the Maori Party candidate.

"That's a much smarter to do than to vote Labour," he said

"It makes sense for them to vote for the party and the candidate and the Maori Party may not get to 5 per cent so they need to win some seats."

However he clarified later his first preference was that those on the Maori roll voted National with their party vote.

English said political stability over the last several years had given this country a consistent economic advantage over many other countries we compare ourselves with.

Seymour welcomed English's endorsement, saying it shows how critical ACT was to centre-right Government.

"Only ACT can keep the ongoing national disaster that is Winston Peters out of power. He goes on about ACT because we've kept him in opposition for the last three elections," he said.

"This is big news, because it means every Party Vote now counts to elect more ACT MPs."

Dunne also welcomed the endorsement for him in Ohariu.

"I am happy to receive support from any who wish to give it, and I particularly welcome the Prime Minister's statement this morning."

He would give his backing to a National-led government after the election.

While he had worked previously with the Clark-Cullen Labour Government "Andrew Little's Labour Party is a shadow of what the Labour Party used to be, and is not ready to govern New Zealand again".