The Ministry for Primary Industries (MPI) has admitted two senior officials made incorrect public statements when explaining why they didn't prosecute over illegal fish dumping.

The matter was only clarified after Newshub laid a complaint with the Ombudsman.

MPI insisted that they couldn't go after illegal fishermen caught on camera in 2013, because their legal advice said they couldn't.

"We did not have the evidence that we could actually lodge a prosecution because we had legal advice that we could not use some of the camera footage," Scott Gallacher, Former Deputy Director General Regulation and Assurance said in May 2016.

"We ended up with a legal opinion that we could not prosecute the fishermen for discarding the fish," Dave Turner, MPI Director of Fisheries Management also said in May 2016.

But no such legal advice ever existed.

MPI now accepts that "the legal advice did not contain a recommendation against prosecution."

Legasea council member Richard Baker says they've misled the public:

"Very unfortunate, but they are now acknowledging that those statements were totally, 180 degrees, incorrect."

MPI says both men were relying in good faith on information that had been provided to them, but that information was wrong, and that "neither had seen the legal advice at the time."

Mr Baker asks "How can that happen? We need answers on that."

The MPI's admission about its legal advice follows an investigation by the Ombudsman that took months.

Auckland University Business School researcher Dr Glenn Simmons has also found it difficult to get information from the Ministry.

"We've faced significant delays and frustrations in getting information and that is something that in our view needs to change significantly."

Despite numerous requests, MPI still won't say who passed on the incorrect information, or how exactly it happened.

It will say only that "human error" was to blame.

Read MPI's full statement following the Ombudsman's investigation: