Live: Prime Minister Bill English says Jacinda effect is explanation for surge in polls

Prime Minister Bill English says the so-called "Jacinda effect" is the explanation for Labour's huge gains in the latest polls.

English told Newstalk ZB's Chris Lynch this morning he isn't worried about Jacinda Ardern's startling increase in the preferred prime minister Newshub-Reid Research poll.

Ardern rose 17.6 points to 26.3 per cent - only just below English on 27.7 per cent.

"The preferred prime minister rating is just part of a package...really what has happened in the last round of polling is Labour have re-gathered up votes they had lost to New Zealand First and, particularly to the Greens," English said.

"I'm quite happy that we have the right team, the set of policies, a great campaign, and we are going to be working hard to lift our support."

Asked if Labour's improved result was down to the "Jacinda effect", English said "that is the explanation".

"They were losing a lot of votes to New Zealand First and to the Greens...under MMP you have to get to 51 per cent. However the votes are shuffled around among those three parties, the election was always going to be tight."

English said on current polling a change of government would require Labour, the Greens and New Zealand First to get together.

"We have to lift our levels of support to get a good government after the election."

Labour increased to 33 per cent in the Newshub-Reid Research poll, with 63 per cent of that support coming from women. National received 54 per cent of its support from men.

When Andrew Little was Labour leader, 55 percent of the party's supporters were women.

The poll comes after Ardern faced media questions about whether she wanted to have children, and her telling broadcaster Mark Richardson it was "unacceptable" for an employer to ask such questions.

"I said what I thought needed to be said and if people rally around that, so be it," Ardern told Newshub.