The Ministry for Primary Industries insists the cameras it is trialling on fishing boats will be used to prosecute illegal fishing.
MPI said a leaked report that rubbished some cameras being trialled was "misleading" and poor quality.
"I want to categorically assure you that the information from the cameras can be used to support prosecutions," said the ministry's acting director of fisheries, Steve Halley.
The leaked report, written by two of the ministry's own forensic experts, said the footage from the cameras being tested in a snapper fishery off Auckland showed the resolution was too poor to identify the species or size of fish - both crucial factors for any prosecution.
Greenpeace has accused Primary Industries Minister Nathan Guy of misleading the public by promising the cameras could be used to prosecute illegal fishing.
Two experts on using cameras as measuring tools, Professor Steve Dawson and Dr Pascal Sirguey, of Otago University, looked at footage from the trial cameras for RNZ.
They both said there was much better, affordable technology than what they had seen was being used on the fishing boats.
The resolution from the trial cameras was too poor to identify fish size or species, just as the leaked report maintained, they said.
But Mr Halley said that was because the trial in that case was to test how good the cameras were for recording legal fish-discarding in bins, and they performed well.
In addition, he said more advanced technology would be put on boats in the industry roll-out next year.
He said tests overseas had shown that technology could identify fish size and species.
The co-author of the report that was leaked, Graeme Bremner, put out a statement last week.
"Without a lot more detailed work of the kind described in the suppressed report ... the ministry will simply collect vast amounts of footage which are of little real evidential value," he wrote.
A former fisheries manager now with the New Zealand Initiative think tank, Dr Randall Bess, was in no doubt where the onus lay for clearing up public confusion.
"It's for MPI and the minister to provide the details that gives the public confidence that they are going to come through."
The 2017 Budget put $30 million towards the new fish monitoring and reporting system. Mr Guy said it would make New Zealand the "most transparent and accountable commercial fishery anywhere in the world".