Masks will be mandatory on all domestic flights in New Zealand, as well as public transport in Auckland, from Thursday.

Prime Minister Jacinda Ardern and Covid-19 Response Minister Chris Hipkins have been speaking after Cabinet met today to discuss whether to make masks mandatory and the exact settings for it.

Hipkins says masks will be required to be worn on all public transport within Auckland, and travelling in and out of the city, and all domestic flights around the country from Thursday this week.

School buses will be exempt as well as children under the age of 12 and some medical conditions, he says.

Taxi and uber drivers in Auckland will need to wear masks, but passengers will not need to wear masks and they will not be required to enforce the rules.

Instead, police can be brought in as a last resort, he says.

"We're not expecting bus drivers to stop the bus and police these measures," he says. Police will be out and about taking an "educate and encourage" approach and will not at this stage be punitive.

Covid-19 Response Minister Chris Hipkins Photo: RNZ / Samuel Rillstone

Mask wearing has so far only been required on planes and public transport at level 2 and above, but a mystery case in Auckland last week meant Aucklanders were asked to wear them on public transport.

Hipkins says the government will also look at whether wider mask use is required nationwide - including on all public transport including buses across New Zealand.

The overall guidance to Kiwis is that when you are in a confined space, you should be wearing a mask, he says, but it is hard to mandate for that so the government is relying on people using common sense.

Hipkins say the government has preserved the good will of New Zealanders during the Covid-19 response and wants to make sure that when mandating mask use, that good will is kept.

"I think what we have seen already in the past three days is that there's a high degree of compliance with mask use."

Ardern says Cabinet today made the decisions to improve the alert level 1 settings, saying despite robust control measures, no system is foolproof.

New Zealand Prime Minister Jacinda Ardern Photo: RNZ / Dan Cook

She says the government has moved to mandate mask use because while management of Covid-19 at alert level 1 has improved, new efforts must be employed to make it safer.

She says on flights, a blanket provision for masks was simpler, given the level of travel in and out of Auckland. The government did not hold back on this decision due to a concern about a lack of public buy-in, she says.

Cabinet will be waiting for advice on whether to extend the restrictions to the rest of the country, Ardern says, and she does not have a date on when a decision will be made.

As for the Covid Tracer app, she says the government wants more people using it and the biggest incentive is a restriction-free summer holiday but the government is "thinking creatively" about how to encourage people to use the app.

Hipkins says privacy is a key consideration around the app, and it is important people stay in control of their data.

Ahead of the decision, Ardern told Morning Report the government had continued to encourage the use of masks, but it was a big difference to mandate something, and she did not take the decision lightly.

However, she supported the move to compulsory mask use.

University of Otago epidemiologist Michael Baker has called for masks to be mandatory on public transport and planes for the foreseeable future.

Covid-19 was an ongoing threat and masks were another valuable "line of defence", Baker said.

After some meat in a coolstore in China which houses New Zealand products tested positive for Covid-19, Ardern says the government was advised yesterday that the positive tests came from beef from Argentina.

She says despite media reports to the contrary, they were not advised that any New Zealand products had tested positive, but New Zealand's government is seeking more information on the testing.

"I want to get to the bottom of this ... this is incredibly important to New Zealand. We are confident, of course, that our products do not and are not exported with signs of Covid on them given our status as essentially being Covid free."

Government too slow to act - expert

University of Otago public health expert, professor Nick Wilson, has been advocating for mandatory mask use since April.

Ahead of the Cabinet decision today, he told Midday Report it was a good idea to mandate mask use on flights and public transport - but it should be applied to the whole country, not just Auckland.

"We really have had way too many border control failures recently, in fact we've had eight since early August, so around once every two weeks. So we've really got to both improve our border defences and have these extra safeguards, such as mask wearing on public transport."

These safeguards needed to be in place until border measures were improved, such as pre-flight testing and pre-flight quarantine, he said.

He also called for a much better smartphone app for contact tracing and the use of other digital technologies to help with contact tracing.

"Other countries are using better systems and we need to learn from them," he said.

"We've been making extremely slow progress in this area, while, for example, Singapore at least a month ago rolled out its equivalent of the Covid card, and places like Ireland have made a much better app available."

Wilson said he knew progress was being made in this area, but it was "way too slow".