Nearly half of New Zealanders don't think Jacinda Ardern's relative youth has any bearing on whether she's fit to lead the country, a new poll shows.

And one in five people believe the Labour leader's age could be an advantage in a 21st-century government.

If Ardern, 37, becomes Prime Minister on Saturday she will be New Zealand's youngest in 161 years.

But 44 per cent of people in a Herald ZB Kantar TNS poll said her age should have no bearing on how voters view her.

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Another 22 per cent said her age could be an advantage as a Prime Minister in a modern government.

On the opposing side, 28 per cent said she was too young and inexperienced as a political party leader to take on the top job.

Older people were more likely to think she was too young for the role - 43 per cent of over-60-year-olds said her age was a disadvantage.

The younger generation was less likely to be bothered about her age. More than three-quarters of 18-to-29-year-olds either said her age was irrelevant or that it was a positive.

Ardern has been an MP for three terms, before which she was a staffer for Labour MPs Phil Goff and Helen Clark, a policy advisor in the UK, and the head of the International Union of Socialist Youth.

When she took on the leadership seven weeks ago, she accepted she was a "young proposition for the party".

But she highlighted her 20 years' experience "in and around politics", nine years as an MP, and a "pretty diverse rural background".

The poll of 1000 people took place between September 13 and 19 and has a margin of error of 3.1 per cent.

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