Several environmental campaigners have told a hearing that a consent to operate the Maui gasfield should be withheld.
They said Shell Todd Oil Services had not cared for the environment enough up til now, and so should not be able to keep on pumping gas from the field.
The Maui field has been producing gas since 1979, but under new legislation Shell Todd Oil Services need approval from the Environmental Protection Authority to keep on drilling.
It wants to be able to do so for another 35 years.
In evidence, Shell Todd Oil services told the authority the rigs' environmental effects so far have been minor, spatially restricted, and transient.
One objector, a former Auckland educationalist, questioned this. Sarah Yates was speaking from Sydney via skype and told the inquiry not enough was known about the impact of this drilling for consent to be given.
"We still don't know enough about the mammals we don't enough about the cetaecians, we don't know enough about the oceans and underwater and I don't see how that can be argued," she said.
"We don't know enough, it's so new."
This view was supported by another environmental campaigner, Caroline Evans, who said New Zealand needed to be cautious.
"If we don't have enough evidence, I feel we should gather more before we continue down the road of allowing permits for another 35 years."
Jean Kahui, of the campaigning group Frack-Free Kapiti, was another objector. She said further development of oil and gas resources was not in the best interests of New Zealand.
Ms Kahui added Shell Todd had not done enough environmental monitoring in the past, and she called on the company to be forced to pay a monetary bond to make sure it does so in future.
"Frack Free Kapiti has provided clear evidence that the company has not monitored or collected data that is useful in monitoring environmental changes and therefore there is every reason to impose significant bonds should a consent be granted."
Several objectors argued that the scheme should be blocked because of the petroleum industry's contribution to climate change, but they were told by one of the commissioners, Sue Powell, that this was not allowed.
She said the law explicitly prevents commissioners from taking climate change into account in hearings like this.
Several objectors said this was not fair, but were told that is the law.
Hearings resume on Monday.
