The Prime Minister says that "any suggestion of borders opening at this point, frankly, is dangerous and I don't think we should put New Zealanders in that position".
It comes after National leader Todd Muller said keeping the borders completely closed for the next year onward was "simply untenable".
In return, Jacinda Ardern said it was instead "untenable to consider the idea of opening up New Zealand's borders to Covid-19".
"In some parts of the world where we have had frequent movement of people, they're not estimating they will reach a peak for at least a month or sometimes several months."
"At this present point of time, our complete focus is ensuring the safety of New Zealanders, while New Zealanders are returning home."
Earlier today, Mr Muller said he was "just making it very clear a shambolic internal border and a strategy that says we stay completely closed to everybody for the next 12-18 months is simply untenable".
"We won't recognise this country in terms of economic impact if that is our reality in 12-18 months' time."
Recent border failures included two people who tested positive for Covid-19 after travelling down to Wellington from Auckland before being tested, and a number of people having left managed isolation without undergoing tests.
New Zealand still has tight restrictions around who can enter the country, but the Government has been toying with the possibility of opening a trans-Tasman bubble with Australia and a bubble with certain countries in the Pacific.
"We've got no visibility in terms of how we would manage the Australian situation, no visibility around the Pacific despite the fact most of those countries are without Covid - they (the New Zealand Government) can't manage the current border situation at all," Mr Muller said.
Ms Ardern said the Pacific leaders she had spoke to "want to move cautiously on behalf of their population".
"That is a theme I’ve heard."
Just over a week ago, Foreign Minister Winston Peters said a travel bubble with certain Pacific Islands was "a matter of weeks" away.
On Australia, Ms Ardern said they would not move to open a trans-Tasman bubble until there was reassurances New Zealanders would be safe.
"We’ve set some criteria as a Cabinet as to what the expectations are and now ultimately it’s up to Australia to decide whether they’ll go for a whole country approach or a state-by-state approach," she said.
Victoria has seen a spike in cases.