Magic Afternoons host Sean Plunket is accusing Climate Strike leader Sophie Handford of "encouraging people to break the law".
The 18-year-old Young Labour member, who has already left school, is in charge of organising the upcoming student strikes around New Zealand calling for action on climate change.
While some schools are open to the strikes, others are treating them as unjustifiable absences, and have warned students there could be repercussions for participating.
Appearing on Plunket's show on Tuesday, the pair clashed over whether the strikes were encouraging illegal behaviour.
"A lot of people are just looking and saying 'lots of kids are just going to wag the day of school'," he said.
"You do know, Sophie, that you're encouraging people to break the law?"
Ms Handford said holding it during school time was the best way to get attention for the climate change fight.
"Kids take a day off school when they're sick, right? And how is this any different?" she asked.
"We have the right to fight for our future. We have the right to a secure future and a safe climate future."
She also denied it was just an excuse for kids to take the day off.
"We are encouraging this to be obviously done in a safe way. We don't want kids wagging and the fact that it's being described as wagging we see as being quite unfair," she says.
"We're actually encouraging kids to get permission from their schools. So lots of kids are doing this as almost like a school trip, so the teachers are taking them out and striking with them."
Plunket had alternative ideas, including agreeing not to go on an OE or not borrowing parents' cars for a week, something Sophie admitted "was an option".
"We're definitively as a group doing our bit to ensure we're walking the talk," she says.