Prime Minister Jacinda Ardern says the Defence Force has been too slow to clean up firing ranges in Afghanistan.
It comes after a Stuff documentary claimed explosive devices left behind may have caused the deaths of seven children in 2014.
Defence Minister Ron Mark says it's not confirmed that it was an NZDF device, as America and Russia also used the firing ranges.
Ms Ardern says she's known about the issue since last year.
The New Zealand deployment to Bamyan Province ended in 2013 and the Defence Force says the firing ranges were cleared to the rules required at the time.
However, the United Nations is calling on the NZDF to take responsibility for the deaths, and military expert Paul Buchanan says the "moral and ethical responsibility" to clean the firing range lay with NZDF, instead of a contractor.
“The NZDF left Bamyan in June of 2013, the range was supposed to have been cleared in October of 2013 by a contractor,” said Mr Buchanan.
“In 2014 the children picked up what was obviously a high explosive, brought it back to the village and it killed seven of them.
He said the NZDF left in a hurry in 2013 which meant they didn’t have time to do the full clearance themselves, which is why a contractor was hired.