Australia's top health official has criticised New Zealand's decision to lift Covid-19 restrictions after seemingly eliminating the virus.

Australia's acting chief medical officer Paul Kelly said today New Zealand should not have returned to pre-pandemic life after going 102 days without community transmission.

He said despite New Zealand's initial lockdown being successful, a return to mass gatherings and lack of social distancing was problematic.

"That is just very dangerous," he told the Australian Senate's coronavirus inquiry today.

"To go right back to a pre-Covid state makes them extremely vulnerable."

Kelly said New Zealand's latest outbreak, which has spread to 30 people, showed why well-performing Australian states must remain vigilant.

"What has happened in New Zealand is a real demonstration of why we have to remain cautious," he said.

Auckland is currently in at alert level 3 lockdown and social distancing measures have been reimposed across other parts of the country.

Prime Minister Jacinda Ardern will announce any changes to those measures at 5.30pm today.