Jacinda Ardern is defending Winston Peters' right to sue government agencies.

The soon to be Acting Prime Minister is taking legal action against the Ministry of Social Development and other parties, for alleged breach of privacy, over the leaking of details of his superannuation payment.

It comes as he prepares to take over from Ardern during her maternity leave.

She told Mike Hosking it's important to distinguish between Winston Peters the minister, and Winston Peters the person.

"It is a decision that he has made not as a minister, he made it before he even became Deputy Prime Minister that he was pursing this issues of privacy, it is a decision ultimately for him."

LISTEN ABOVE AS JACINDA ARDERN SPEAKS WITH MIKE HOSKING