Prime Minister Jacinda Ardern has decided to delay the election until October 17.

Announcing the decision this morning, Ardern said the re-emergence of Covid-19 in the community was a cause for concern during the election period.

And while the Electoral Commission said voting could safely happen under alert level 2, Ardern said she also had to factor in participation of voters, fairness and certainty.

Under normal circumstances, the election date rests solely on the Prime Minister but Ardern said moving the election was a significant decision so she consulted other political leaders.

She considered complete consensus was unlikely but all agreed on certainty.

She considered retaining the current date, moving it until October 17 and November 21, and decided on October 17.

She was advised the date was achievable and the Electoral Commission would be able to draw on some of the work they'd already done.

Having early voting start during the school holidays had the downside of some people moving around the country and impacting the Commission's workforce but meant there would be some additional facilities available.

Parliament will reconvene tomorrow. The dissolution of Parliament will now be Sunday September 6th. The Governor-General has been advised of the new date.

Ardern said Covid was the "world's new normal" and gave the assurance she wouldn't change the election date again.

• Pressure mounts on PM to delay election; National, NZ First back calls
• Political scientist: Election campaigns already moving online
• Winston Peters joins calls for election to be postponed

"Covid will be with us for some time to come. Continuously pushing out an election does not lessen the risk of disruption and this is why the Electoral Commission has planned for the possibility of holding an election where the country is at level 2, and with some parts at level 3.

"I have absolutely no intention at all to change from this point."

Pushing an election out by several months didn't mean disruption was less likely, said Ardern.

A Herald-Kantar poll this morning revealed 60 per cent of New Zealanders did not think the election should still be held on September 19 - but opinions differed greatly between Auckland and the rest of New Zealand.

Ardern said she accepted a sense of anxiety, including from political parties, about the disruption to the start of the campaign period.

Ardern said she never considered a vote of no confidence was a threat because that would have triggered an election.

She said even if she didn't pick up the phone and talk to anyone, October 17 was her preference.

Asked what would happen if New Zealand went back into alert level 4, she said: "I'm not anticipating that at this stage. There is no evidence that that is where we would be."

Ardern said she considered what would maximise voter turn out.

Ardern said the referendums didn't impact her decisions.

She said there were "many, many knock-on effects" to delaying the election, including to electoral workers and candidates who'd taken leave without pay to campaign, but she believed New Zealanders deserved certainty.

Ardern said at no point during her discussions with political leaders did she give any indication of her preference on the date - including with her discussions with NZ First leader Winston Peters.

Labour won't launch their campaign again, said Ardern.

It will be up to individual political parties about whether they suspend their campaigns, she said.

Ardern is getting advice from Crown Law on spending caps for campaigning.

National, Act and NZ First had all called on Ardern to delay the election, saying the September date made it difficult for political parties to campaign, and that voters would be wary of voting.

Green Party co-leader James Shaw this morning said "a change to the election day should occur because it is what is best to keep us safe and protect our democratic right to vote. We believe the date change to October 17 achieves that fine balance during a very challenging time".

Co-leader Marama Davidson said "we support the Prime Minister's decision to move the date to October 17. Those additional four weeks should provide time for the public health response to get on top of the current outbreak".

Peters welcomed the Prime Minister's decision.

"New Zealand First is pleased that common sense has prevailed. We were concerned that the Covid outbreak had the effect of limiting campaigns to an unacceptably short period until overseas and advance voting begin if the general election was held on September 19."

Yesterday, there were 12 new cases in the community and one in managed isolation. All of the 49 active community cases could either be definitively traced to the Auckland cluster or were under investigation but considered likely to be connected.

Three people were being treated in hospital.