Authorities are increasingly concerned that walkers are setting out on the Tongariro crossing in the central North Island without appropriate clothing, fitness or information.

The helicopter rescue of a woman injured on the crossing on Sunday has added to police and Department of Conservation concern.

The crossing, in Tongariro National Park, has been called "the best one-day walk in New Zealand", a slogan DoC wants to change, said Lianne Fraser, DoC's Turangi-Taupo area community relations manager.

"The Tongariro crossing is an extending 18km trek over steep volcanic terrain - it is not a jaunt in the park," she said.

The weather could change with alarming speed and DoC workers often felt at their "wit's end" when people ignored advice.

"I've seen people struggling in high winds and sleet with flimsy plastic rain ponchos which offer zero protection from the elements."

Mrs Fraser said there was little or no cellphone coverage in the area of the crossing.

"Frankly, it's amazing that more people aren't injured or killed."

DoC estimates that between 500 and 700 people walk the track at peak periods.

The crossing is generally walked from Mangatepopo to Ketetahi and takes seven to eight hours.

- NZPA