Police have criticised a tour operator for dropping off a group of tourists to walk the Tongariro Alpine Crossing on Saturday when weather conditions were hazardous.
Sixteen trampers who police say were ill-equipped and not well prepared eventually had to be rescued.
Police say tour operator Kevin Gardiner from Mountain Shuttles dropped the group at the Mangatepopo car park at the start of the 19km walk, telling them the poor visibility, rain, strong winds and very cold temperatures would improve.
Police say Mr Gardiner was irresponsible, as the group were inexperienced, lightly-clad and the early stages of hypothermia were setting in when two trampers came across them and raised the alarm.
But Mr Gardiner says the forecast was for improving conditions on Saturday and the group were told this and given the option of turning back. He says all the group were adults and could make their own decisions.
Another operator, Gus te Moana, says his company Hotbus refused to take people onto the track on Saturday because of the weather. He says he is surprised to hear that Mr Gardiner did, as he is an experienced operator.
Brent Guy, from the Conservation Department, told Radio New Zealand's Checkpoint programme on Monday the Tongariro crossing is no different than walking in the Southern Alps and warm gear is essential - regardless of the time of year.
"The weather forecast was marginal, to say the least. It was for improving conditions on Saturday afternoon, but it's never guaranteed in the alpine areas. And once you're wet and cold, it is very, very difficult at 1900 metres above sea level to get warm again."
Mr Guy says about 80,000 people walk the crossing each year and there are relatively few rescues.