Opposition parties react to alert level announcement

National leader Judith Collins says she has to trust the Prime Minister made the right call about extending the alert levels because she hasn't seen Cabinet's advice.

And Act leader David Seymour has taken aim at the contact-tracing systems, saying they've got behind the virus and called for more accountability.

Collins said she understood the four-day extension of alert level 3 in Auckland would be tough on small businesses, especially hospitality, and her thoughts were with them.

But Collins couldn't say what National would do differently - including extending the wage subsidy - because they hadn't seen the Government's advice.

"We just have to trust the Prime Minister has thought that one through."

Collins said she wasn't consulted by Jacinda Ardern before the announcement this afternoon and it had been about a week since National's health spokesman Shane Reti had a briefing.

"The Government's got its own advice on this and we don't have that so we just have to take the view that the Prime Minister has taken the best advice and made the right call because we haven't seen anything else to say otherwise."

But she welcomed the move to make masks mandatory on public transport, planes and in taxis and Ubers from next Monday, saying "it was a no-brainer".

"People have had mixed messages on that so it's good to see that the Government has finally done that."

Act leader David Seymour also supported making masks compulsory in some situations as his party's position was for a proportionate reaction to the public health risks.

"In the case of an epidemic, clearly our species is under attack and we need to defend ourselves against it."

Seymour said the Government failed to use "the fair weather to mend the roof of a storm that was coming" by not investing in better contact tracing systems.

Ardern had "no choice" but to extend alert level 3 in Auckland because the "virus is getting away from the contact tracing" and the Government hadn't invested in a smarter approach, he said.

Even if there was a one in 10 shot of the $100 million CovidCard technology working, Seymour believed it would still be cheaper than the economic impact of extending Auckland's lockdown.

He also took issue with there not being a clear line of responsibility for the outbreak.

"The lack of accountability is staggering, the Prime Minister refuses to blame anyone but now she's blaming the trickiness of the virus.

"Well no one's talked to me like that since I was at Hora Hora kindy in 1987. It's trickiness that's to blame? Give us a break."