A group of academics say a government agency holds more than 100 reports into alleged fish dumping and catch misreporting but is refusing to make them public.
The researchers, from universities at Auckland and Oxford, England, have gone to the Ombudsman to seek the release of the information, which they say is vital to their work on the fishing industry.
Glenn Simmons and Nigel Haworth, from the University of Auckland, and their international colleague Hugh Whittaker, from the University of Oxford, say they first applied for the reports in 2015.
In an opinion piece written for the Herald they said their request was first refused by the Ministry of Primary Industries (MPI), so they refined it to 14 named reports, but that is yet to be answered.
"[MPI] is still refusing to release internal reports relevant to our ongoing research, many detailing the ministry's own investigations into reporting and dumping," they wrote.
"This not only obstructs academic research. Transparency is the only way we can get to grips with the problems facing the fishing industry."
Their complaint comes a day after Greenpeace went public with its complaints about the close relationship between the industry and the Government - revealing the MPI had outsourced a swathe of monitoring to an industry-owned company named FishServe.
Greenpeace first learned about the connections when applying to the ministry for data under the Official Information Act and being redirected to FishServe, a paid service. It refused to apply to FishServe, and is still awaiting a response.
A spokesperson for the MPI said the agency took its responsibilities under the Official Information Act very seriously.
It said it withheld the reports under "provisions in the act". It said it was not appropriate to share the reasons for withholding because they were the subject of an Ombudsman's investigation.
"The wider context is that MPI has already voluntarily released large amounts of information related to the Heron report, including internal emails, and opened itself up to an independent external review," it said.
"These are not the actions of a ministry that is hiding information from the public."
The report by Michael Heron, QC, was completed last year, and found the 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, the 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.
The Ombudsman confirmed it was investigating the recent complaint about the documents, named by the researchers as 14 reports on operations Apate; Apate II; Blade; Box II; Bronto; Horse; Kenwood; Mega; Mini; Maxi; Purse; Trios; Turn Up; and Uzi.