While Jacinda Ardern has promised a "relentlessly positive" election campaign, she's been warned not to expect the same from the Opposition.
The Prime Minister was asked on The AM Show on Thursday if she expected a "dirty" election campaign.
"Not from our side," she told host Duncan Garner. "I can't predict how others will behave."
Labour and the Greens have signed up to Facebook's Ad Library, where users who see their ads will be able to also see who is behind it, how much money is being spent and why they were targeted. National's potential coalition partner ACT has too, but National hasn't.
The Ad Library was set up in response to a slew of ads run by Russian trolls during the 2016 US election campaign, designed to look like they came from US-based groups.
"I'm going to encourage that we keep this a Kiwi campaign - New Zealanders expect a certain kind of level of sportsmanship," said Ardern. "That's just us. So why shouldn't that cross over into politics?"
AM Show sportsreader Mark Richardson, who represented New Zealand in 38 test matches in his professional cricketing career and is a National Party supporter, suggested Ardern was making a mistake.
"Sportsmanship is actually fictitious as a concept," he told her. "You give a sportsman half a chance and he'll take what he can."
"Not all of us," Ardern shot back.
National's recent advertising on social media has come in for criticism, with statisticians taking issue with misleading graphs the party has used to show costs of living rises under the present Government, and the Advertising Standards Authority upholding multiple complaints against the party.