New Zealand Prime Minister Jacinda Ardern has shown her compassionate side again during a recent visit to a supermarket.

Ardern confirmed that she recently helped a mother-of-two who had forgotten her wallet while out shopping at a Countdown store in Ponsonby, Auckland.

In a Facebook post, the mother wrote, "Just when you think Jacinda Ardern couldn't get any more lovely, low key and authentic ... she goes and pays for your groceries at the supermarket, because you've got your shopping, have two kids with you and are about to put it all back as you forgot your wallet."

When Ardern was asked by a journalist during a press conference on Thursday whether she had paid for the woman's groceries, she said, "Yes."