Expert witnesses' primary duty is to the Environmental Protection Authority and not the companies that hire them, the authority says.
Early hearings of the authority were widely criticised by mining and oil companies for being bureaucratic and expensive.
A common theme was that experts hired by applicant companies, often at great cost, were then appropriated by the authority itself, which did not pay good money to hire experts of its own.
And an authority executive, Richard Johnson, has told a mining conference in Wellington that this policy would continue.
He said experts who signed up to a code of conduct devised by the Environment Court did not have the option of advocacy for their employer.
"For a lot of people in the seabed mining area the role of experts is a little bit odd for them," he said.
"They say that, 'I'm paying for them, therefore they will be my advocate'."
But this option was not available.
"If they (the experts) sign up to the code of conduct they are not there to do advocacy but to be an expert in their subject matter.
"They are there to look at the facts of the matter and drive to areas of agreement and disagreement," Mr Johnson said.