Prime Minister Jacinda Ardern is pushing back at National's claims that the mismanagement of the country's borders will hit growth and cost jobs during the recovery from Covid-19.

National is criticising the government's mishandling of the border saying it will cost New Zealanders jobs, by damaging the economy and delaying the reopening of the country.

Economists generally agree that unemployment could spiral to unprecedented levels if New Zealand were to enter lockdown again.

National's finance spokesperson Paul Goldsmith told Morning Report that an effective testing scheme at the border is linked to improving the state of our economy.

"If people are fearful that the border is not well managed then that will be delayed and of course every week and every month that is delayed will cost jobs."

He said bringing back foreign students is crucial and he wants to see the borders open as safely and quickly as possible.

"What I'm talking about is the need for confidence and New Zealanders will be naturally fearful if they don't think it was properly managed and they keep hearing stories of the rules not being followed ... for goodness sake restore the confidence."

Ardern told Morning Report that all the way through the pandemic, the opposition has called on the government to be more liberal about letting people in at the borders and she has pushed back against that.

She disagreed that the recent revelations about a slack approach to supervising managed isolation was costing the country jobs. She said Covid-19 is still a pandemic that is growing internationally with 8 million cases and over 100,000 cases emerging a day around the world.

"We have to continue to take a rigorous approach so I make no apology for that. Their calls for opening the borders and being more liberal at the borders - now is not the right time.

"Most countries continue domestically to battle this virus . We happen to be seeing it in our quarantine facilities as opposed to our general community, so we are in a privileged position."

She said there is no need to reduce the number of countries people are returning to New Zealand from.

The number of people returning has doubled since last month and there are flights from countries that hadn't been connected earlier, including high-risk countries.

There are now around 4270 people in 20 facilities, Ardern said.

She said a large number of staff overseeing them, with a doubling of Defence Force staff in recent days, more police and also aviation security staff. Tests were being carried out at day three and 12 and there were daily health checks on all those in isolation. The country still had under 10 positive cases in a week, while Australia had just announced 19 in one day.

"We are seeing them in quarantine where we are set up for cases to emerge. ...We treat all those 4000 as if they have it."

Some travellers were bussed to a hotel in Rotorua at the weekend because Auckland hotels are now full. It was always the plan to look at other centres from this week, Ardern said, however, there were robust criteria applied to any facility that is chosen.

"We don't take over a facility until we absolutely consider it to be appropriate which is one of the reasons we didn't take one over in Auckland recently. It didn't meet Commodore [Digby] Webb's expectations."

Ardern said she was expecting to see the results of Air Commodore Webb's audit of the way facilities were being managed this week.