The government says it will consider funding the GeoNet quake monitoring service for 24/7 staffing.
GeoNet director Dr Ken Gledhill said the service needed around the clock staff to make vital decisions about tsunami threats.
A spokesperson for Acting Civil Defence Minister Gerry Brownlee said extra funding for the monitoring centre to be staffed 24/7 would be considered as part of a civil defence review.
Dr Gledhill told Nine To Noon the early warning system worked well for the most part in the 7.8 magnitude earthquake that hit near Hanmer Springs at 12.02am on Monday.
He said because GeoNet was not staffed overnight or on weekends it was unable to provide tsunami warnings as quickly as he would have liked.
"The best practice is to have someone who is awake and ready to respond straight away, he said.
"And that's a human being, not a machine.
"The machines are doing most of the work, but there's a human being for the final decision."
At night and the weekend there are two duty people, in Wellington and Taupo, and they were woken if there was a major event, he said.
Prime Minister John Key said tsunami warnings would be looked at as part of the civil defence review.
"They are locally dictated, and anyway, I think every New Zealander needs to follow the very clear instructions, which is if an earthquake is long and strong and you're by a coastline, act quickly.
"Because sometimes even with the best tsunami warning systems in the world, you won't get out fast enough unless you take very fast action," Mr Key said.
Labour Party leader Andrew Little said the alert system should be changed now.
The warnings on Monday morning were confusing and ad-hoc, and the centre should be manned around the clock, Mr Little said.
Given the events of the last few years, GeoNet should be funded urgently, he said.
"We are a country that is built on tectonic plates. Earthquakes happen, and when they happen seriously, as they have done this week, there's a threat to life and limb and buildings.
"We need an agency monitoring that stuff 24 hours a day."
The government has said it was looking at a national tsunami alert system, but any decision was sometime off.
Dr Gledhill said he would continue to push for better support and resources for GeoNet so the information distributed to New Zealanders after geological activity was accurate immediately.
"All New Zealanders have to be aware of what the environment they are living in is. And this is it. We live in the shaky isles, we live on a plate boundary."
His team refer to the "GeoNet community", which he said came out of the Canterbury earthquakes and encompassed everyone from people on the street to high-level scientists and politicians.
"I see it as our mission to educate and instil knowledge to people about the world we live in and that means we can live in it better, more happily."