"I think it's a legitimate question for New Zealand, because she could be the prime minister leading this country", Richardson said, referring to Ardern's possible role if she pulls off a dramatic reversal of fortune for the opposition party.
Ms Ardern, who is dating media personality Clarke Gayford but does not have any children, pointed her finger at Richardson as she flatly rejected his reasoning. She added, "For me, my position is no different to the woman who works three jobs, or who might be in a position where they are juggling lots of responsibilities".
A New Zealand politician has slapped down a male radio host for insisting the country has a right to know her pregnancy plans, labelling the question "totally unacceptable" in 2017.
"I've got a question and we've been discussing today whether or not I'm allowed to ask it", said Mr Mulligan before proceeding. It is the woman's decision about when they choose to have children.
She also pointed out that male politicians and employees are nearly never questioned about their family planning, saying, "Would you ask a man whether or not they are likely to have kids in the future?"
If successful in the September 23 election, Ardern could become the country's third female prime minister.
Richardson asked Ms Ardern, who does not have children, whether she thought it was "okay for a PM to take maternity leave while in office".
Have you been asked questions about your gender, age or marital status that lead to probing questions about your intention to have children?
This isn't the first time Ardern's been asked about her parental plans.
Jacinda Ardern, who was appointed the leader of the Labour party on Tuesday, has less than two months before the next round of elections.
Ms Ardern, visibly angry with the question, said New Zealand women had a right to keep their child-bearing plans private from their employers.
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Even English jumped in, saying the questioning was unacceptable. You've just got to take every day as it comes and try to make the best of the lot that you're given. She was voted in as leader after Little bowed out due to a series of devastating polls for the party. She was chosen to lead the opposition just weeks before a general election in an effort to boost support for the Labour Party, which is now trailing English's National Party.
Current Prime Minister Bill English has six children.
"The real problem for her is the Labour Party and its lack of progress over nine years in opposition - in the end, that's what put the pressure on Andrew Little", he said.