New Zealand's newly-elected Labour leader Jacinda Ardern has gone from strength to strength.

The country's election next month was expected to result in a resounding win for the incumbent conservative National Party Government, which has been in power for almost a decade.

But in the three weeks since being elected, Jacinda Ardern has revived Labour's moribund primary vote.

Like the Australian Labor leader Bill Shorten, she has been emphasising fairness and equality — promising to tackle the increasing gap between rich and poor, and child poverty.

Now most polls and political pundits are putting Labour neck and neck with the Prime Minister Bill English and his party.