There are calls for further investigation into the Government's response to illegal fish dumping - with opposition MPs saying they feel misled by the Ministry for Primary Industries.
Both Labour and the Greens said they believed MPI had been "captured" by the fishing industry.
Parliament has gone into urgent debate this afternoon on the matter of fisheries management, following a report into officials' decision not to prosecute those caught on camera dumping tonnes of healthy fish.
Labour MP David Parker said the initial response from MPI to reports of dumping was dismissive and highly defensive.
"I feel very misled ... I think we need to question those ministry officials and get to the bottom of this with some further independent scrutiny of what has been going on in MPI."
On Friday, the findings of a high-level inquiry into the decision not to prosecute commercial fishing boats which were caught on camera dumping tonnes of healthy fish in New Zealand waters were released.
The inquiry, led by QC Michael Heron, said the MPI obstructed the prosecution process, that its decision process was "confused", and that it failed to follow up and "draw a clear line in the sand" with regard to fish dumping.
Parker said the amount of illegal fish dumping happening in New Zealand waters was likely to be "enormous". The Heron report suggested "the ministry may have been captured by industry interests".
"Was it some isolated person making a mistake in the ministry? No. This went up very senior in the ministry."
Green MP Eugenie Sage said an independent inquiry was needed. The Heron report exposed the "very sorry tale" about the way MPI operates.
Fish dumping not only resulted in fish being wasted, she said, it meant information used to set catch limits to ensure sustainability was wrong.
"And yet we have the ministry keeping this quiet - it wouldn't have come into the public domain if the Operation Achilles report hadn't been leaked."
NZ First MP Richard Prosser said his party had called for a commission of inquiry in June.
Recreational and commercial fishers needed certainty, he said, and the current quota management system was causing problems.
"Fishers know that landing catch outside of their quota is going to cost them, so they dump it."
Primary Industries Minister Nathan Guy said he welcomed the recent Heron report and also today's urgent debate.
It was regrettable that the fishers involved could not be held to account, Guy said, because of the limitation period for prosecution.
The Heron report noted that MPI prosecuted hundreds of cases a year, and the processes were generally robust and people involved professional, Guy said.
A raft of changes including fast-tracking more electronic monitoring equipment on boats were being made within MPI, he said, and the law would likely need to be changed to enable better prosecutions.
"[But] the industry needs to pull its socks up. Because at the heart of this issue are fishers.
"My challenge to the commercial sector is they need to pull their socks up and get onboard with these changes. Because if they don't, our international reputation will be tarnished."
Labour MP Kelvin Davis rubbished those comments.
"He says, 'I've told the industry to pull up their socks'. Hmm ... I was a school teacher for 20 years and when I told kids to pull up their socks, that was an invitation for them just to get their socks down."
As a keen recreational fisher who knew he was liable to get punished for any breach of the rules, Davis said it made his blood boil to look at the footage of illegal fish dumping.
"What happens to them? Nothing. Why is that? Because these commercial fishers are the mates of this government."
The ministry-commissioned inquiry was launched in May following reports that MPI had chosen not to prosecute local fishing captains who were caught on CCTV cameras dumping healthy-sized fish.
Heron looked at three separate investigations into dumping in 2003, 2012 and 2013, known as Operation Overdue, Operation Achilles and Operation Hippocamp.
Operation Achilles, in November 2012, discovered that five out of six vessels operating off the eastern coast of the South Island had discarded quota fish - mostly gurnard and elephant fish. Between 20 per cent and 100 per cent of quota fish were being thrown out with every haul.
However, despite a recommendation by the investigator, MPI did not proceed with a prosecution and instead issued a warning to the boats' skippers.
This decision, and the process leading up to it, was flawed, Heron's report said.
An internal email written by MPI's director of fisheries management, and released as part of the report, stated, "fish dumping is so widespread that the current system is failing and officials have not been able to get on top of it from day one of the quota management system.
"We estimate that if we found the golden bullet to stop discarding, we would probably put over half of the inshore fleet out of business overnight."
Guy has said that view was a personal one and was not backed up by evidence.