New Zealand Prime Minister Jacinda Ardern says mortality rates were enough for her to push past civil liberties concerns in her government's eye-catching new Smokefree 2025 plan.

The plan, which aims to get smoking rates down to five per cent by the middle of the decade, captured enormous attention around the world after its launch on Thursday.

To get there, NZ will water down the nicotine content of cigarettes - thought to be a world first - and drastically cut the number of stories that can sell them.

The most radical proposal is the creation of a "Smokefree generation" by stopping anyone born after a certain year from ever buying cigarettes.

"When I saw what the BBC had picked it up, 'I thought, yeah, I can see why'," Ms Ardern told AAP from her Wellington office on Friday.

"For the outside looking in, a Smokefree generation captures the imagination.

"When we discussed this in cabinet, it wasn't lost on us that it was it was groundbreaking.

"But if you say, 'Does anyone object to the idea of preventing children (from) picking up a cigarette? Would anyone object to the idea of stopping a young person from taking up something that they had a 50 per cent chance of killing them?

"When you present it like that, who wouldn't want to prevent a child from doing that?"

The cigarette-buying ban will mean anyone born in 2011 or later will never be able to buy them.

Opposition parties have attacked the policy suite, suggesting prohibition will cause other challenges, but public health experts have been unanimous in their praise.

"It's truly a game changer ... New Zealand once again leads the world," Natalie Walker, University of Auckland population health associate professor, said.

"The proposed combination of policies is perfect."

Chris Bullen, public health professor at the University of Auckland, was just as effusive.

"All I wanted for Christmas this year was evidence of a serious commitment from government to tackle our tobacco smoking problem ... all my wishes have come true," he said.

"If implemented as outlined, it could just be the single most significant step we take as a nation to reducing preventable death and disease and reducing health inequities in the next few years."

The plan is in keeping with the government's well-known focus on public health above other priorities, best displayed through its hard-as-nails approach to COVID-19.

NZ successfully eliminated the virus in 2020 as it raged in other countries, and is keeping borders shut to the rest of the world until at least May as it tackles a Delta outbreak.

Ms Ardern said the experience helped her shrug off protesters.

"I've been around politics a long time ... and I still do all my own social media," she said.

"(Fringe elements like anti-vaxxers) has always been there. There's just a particular rallying point at the moment. So I keep it in perspective.

"Here, we just focus on making something that works for us."