In contrast to New Zealand, which entered a severe lockdown last week, Australia is yet to reach the same level of self-isolation as the government favours more freedom of business and of movement.

Mr Key likened the Australian trajectory to that of the United States, where more than 142,000 Americans have contracted COVID-19 and almost 2,500 have died.

"The United States is having big numbers and probably Australia (will be) having pretty big numbers frankly, following a different path to us," he told radio station Magic Talk.

The downside of New Zealand's unprecedented shutdown of business is the economic and fiscal toll.

The government has already legislated for over $NZ56 billion (SNZ55 billion) of support to business and individuals as it keeps business afloat and food on the table of Kiwis who have downed tools.

Mr Key, who led a conservative National party government from 2008 to 2016, said the economic price could be "really ugly" but backed the approach of Jacinda Ardern's government.

"The efforts the government is making are the right ones," he said.

"Putting cash into banks ... the mortgage holiday, right through to wage subsidies right through to the working capital program.

"That won't save every job but it will help transition things ... I'm a little bit more optimistic than the worst case scenario."

Completing his praise for Ms Ardern, who leads the rival Labour Party, Mr Key praised Ms Ardern's "outstanding" communication during the crisis.

"She communicates really clearly and really well," he said.

Ms Ardern said she "kept an eye on what Australia is doing" but as New Zealand didn't have a a state-federal governing mix that necessitated Australia's National Cabinet, New Zealand could move more swiftly.

"The starting point is the comparison is different. It's much easier for us to move as a nation of course because of our system and the way we're organised," she said.

"I noticed that they have been moving further and further up in terms of their restrictions."

Ms Ardern and Australian Prime Minister Scott Morrison stay in close contact and spoke on Monday morning, comparing notes on the coronavirus.

That conversation allowed the Kiwi PM to again petition Mr Morrison to provide welfare support for her citizens in Australia.

"It is a group I am concerned about," she said.

"I think it's ultimately a matter for the Australian Government, but it won't stop me from from raising the issue."

On Monday, health officials announced 76 new cases in the past 24 hours, bringing New Zealand's coronavirus infection tally to at 589 people.

One New Zealander has died in the pandemic, an elderly South Island woman who had underlying health risks and who was mis-diagnosed with the flu on her arrival to hospital.

Australian Associated Press