The Prime Minister has responded after Australia accused New Zealand of being a soft-touch for people smugglers.
Malaysian police intercepted 130 Sri Lankan asylum seekers over the weekend- and the Australian government alleges they were heading for New Zealand.
Australia's Home Affairs Minister Peter Dutton says New Zealand being "marketed as a definite destination".
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"Those people cannot come to our country unless they're issued with a visa, and it's a very different story if you're coming out of Auckland or Wellington - you can jump on a plane into Sydney, Brisbane, and then claim protection or whatever the case might be," he says.
Ms Ardern told host Duncan Garner that Kiwis should be sceptical of people smugglers' claims.
"There have been those who have claimed they're heading to New Zealand but actually it's clear their destination is Australia," she says.
"It's not new, but it shouldn't change the fact we need to be vigilant."
Green Party immigration spokesperson Golriz Ghahraman has accused Mr Dutton of scaremongering.
"There's no evidence other than him making these comments," she says.
"And it's something he started doing around the time that our Prime Minister essentially embarrassed his Government."
When former Prime Minister John Key changed the law in 2012 to detain so-called "boat people", Labour said they were scaremongering, expressing doubt that any of these vessels - which it labelled 'ghost ships' - could make it to New Zealand.
Ms Ardern wouldn't disclose whether she has been briefed on if a boat could reach New Zealand, but warns it would be a "dangerous venture".
"We don't want them to try," she says.
"This is the most treacherous stretch of water in the world. Even those who may perceive that they've got a capable boat would risk lives in trying."
She says New Zealand is targeting the people-smugglers by investing in preventive measures.
"The most compassionate approach we can take is the approach that says no person seeking to smuggle people should ever leave a port," she says.
Watch the full interview with Jacinda Ardern above.
The AM Show with Duncan Garner, Amanda Gillies and Mark Richardson, weekdays 6-9am on RadioLIVE and streaming live to the rova app on Android and iPhone.