Prime Minister Jacinda Ardern and Mike Hosking have gone head to head, debating the Prime Minister's press-conference language that the level 4 lockdown is extending only "two business days", when some retailers and outlets are missing out on five days of trade.

The Newstalk ZB host challenged Ardern's language this morning as Opposition leader Simon Bridges and the retail industry warned that many small businesses faced closure, even with new level 3 rules coming into effect from 11.59pm on Monday.

They say the new rules are still too restrictive and cannot understand why retailers can't open with the same health and safety precautions as those followed by supermarkets in the past four weeks.

Ardern yesterday announced the lifting of level 4 in a week's time and that level 3 would be in place for at least two weeks.

Bridges said he had spoken to many small businesses that now faced closure. "At four weeks they could survive ... at seven they can't," he told Newstalk ZB.

Ardern told Hosking she had heard from some Australian leaders that they had wished they had followed New Zealand's example and tightened shopping restrictions - many retailers were doing it tough because no one was out and about shopping, yet they still had to pay wages.

The pair debated the reference to the lockdown only extending by "two business days".

Hosking: In what world is Thursday to Tuesday two business days and no one seems to open on a Saturday?

Ardern: That's not to diminish that people obviously work weekends. That tends to be often ... if you put retail and hospitality in those groups. Obviously in alert level 3 they are impacted differently than everyone else who is returning to work. I don't diminish that. In the world where you have public holidays and weekends, that was my reference to two business days.

Hosking: For business people who can't open, it's five business days.

Ardern replied that by and large she had seen general acceptance of the strategy from the likes of business leaders and industry groups. They had welcomed the balanced approach, she said. She also said retailers could prepare now to operate online under level 3.

Hosking: At least you could concede it's five business days not two because no one believes you. If I was a business opening under level 3 I would have traded on Thursday and Friday and Saturday, and Sunday and Monday.

Ardern: What business are you Mike? For this hypothetical situation that we are talking through, because retail cannot open at level 3.

Hosking: McDonald's.

Ardern: If you want to make the argument that I wasn't properly referencing the drive-through or takeaways, sure. What we are talking about for many individuals who are thinking about public holidays and weekends ... two business days is language we use commonly to refer to Monday to Friday.

Hosking: Only in Wellington - not in the real world.

Ardern: Do you work weekends, Mike?

Hosking: I don't but I have worked weekends and I do work on the weekends, yes. So I consider I probably work seven days.

The interview comes as the number of worldwide cases of Covid-19 nears 2.5 million, with almost 170,000 deaths and 650,000 recoveries. The United Kingdom faces another four weeks in lockdown - with 16,500 deaths but optimism that the infection rate is slowing.

Australia's state and territory leaders will meet with Prime Minister Scott Morrison today to discuss a potential end to lockdown measures in the country. It comes after states have recorded lower numbers of daily cases and reports Australia has managed to contain the outbreak.

Australia has recorded 71 deaths from Covid-19 so far, with 6617 confirmed cases in the country.

Under the lockdown decision announced yesterday, Kiwis will be able to pick up takeaways in a week and may be able to socialise more freely in three weeks' time.

But many retailers are unhappy they cannot reopen physical stores with the same health and safety precautions as those followed by supermarkets over the past four weeks.

While Retail NZ chief executive Greg Harford believes some businesses will be able to trade in some form online, many are still hamstrung.

It was disappointing, he said, that a broader range of stores could not reopen their physical outlets, following health and safety rules such as queue management. Many would go to the wall.

Under alert level 3, there cannot be any contact for shoppers. That means retail has to be contactless with purchases and deliveries.

Shopfronts cannot be open to customers, with the exception of supermarkets, dairies and petrol stations.

Canterbury Employers' Chamber of Commerce chief executive Leeann Watson said it was "almost impossible" for the retail and hospitality sector to function under these restrictions and more support was needed from the Government.

"This reinforces the need for some intervention for retail and hospitality because it is incredibly difficult for them to have any normal trade under alert level 3," she said.

"Some businesses will be able to operate online but not all of them will be able to and certainly not to full trading capacity."

Ardern announced the much-anticipated decision after deciding that silent community transmission was unlikely to be happening in New Zealand.

"The effort of our team of five million has broken the chain of transmission and taken a quantum leap forward in our goal to eliminate the virus," she said.

Ardern chose to extend the lockdown by five days until the end of Monday to minimise the chances of returning to alert level 4 in future.

It comes at an economic cost of two business days instead of three due to Anzac weekend, but Ardern said it was worth it to be more certain about eliminating Covid-19.

That extra certainty will come from a ramping up of contact-tracing capacity, and tens of thousands of extra tests in remote communities or around cases where the source of infection remains a mystery.

The Cabinet's decision was welcomed by public health experts and businesses seeking clarity about future operations, although the former had concerns about schools and ECE centres opening and some of the latter wanted the lockdown lifted earlier.

When alert level 4 is lifted at midnight on Monday, April 27, New Zealanders would have spent 33 days living with unprecedented restrictions on movements and activities.

Ardern asked New Zealanders to remain lockdown compliant, but businesses were now allowed to return to their premises to prepare to reopen.

Schools and Early Childhood Education centres were also allowed back on premises to get ready for a teacher-only day on April 28 - the day after lockdown ended.

Police will still be out in force asking people to justify away-from-home movements.

Alert level 3, Ardern warned, will see similar restrictions on people's social lives, and schools will be open but children were asked to stay at home if possible.

But 400,000 to 500,000 more workers will return to work.

On May 11, the Cabinet will assess whether the country is ready to move to alert level 2 on May 12.

Ardern said that extending the lockdown was also recommended by Director General of Health Ashley Bloomfield, even though there was high confidence that undetected coronavirus outbreaks were not happening.

Several signs indicated this including a low transmission rate of 0.48 (meaning an infected person on average infects less than half a person), low per capita cases, and one of the lowest mortality rates in the world.

New Zealand also now had one of the highest per capita testing rates in the world, and since April 1 there have been only eight cases where the origin of infection was unknown.

Yesterday there were nine more cases of Covid-19, the same number as the previous day.

There are now 1440 cases, with 14 in hospital and three in ICU, two of whom are in a critical condition.