Two former members of the panel charged with reviewing the salmon industry's expansion into Storm Bay raised concerns with the body's chairman prior to resigning, new documents show.

Key points: The aquaculture and environmental management experts raised concerns with panel's chairman before quitting

The aquaculture and environmental management experts raised concerns with panel's chairman before quitting The reasons for their resignations were detailed in a letter to Primary Industries Minister Guy Barnett

The reasons for their resignations were detailed in a letter to Primary Industries Minister Guy Barnett The letter obtained through a Right to Information request was almost entirely redacted

However, a letter detailing their reasons for ultimately quitting the panel has been almost entirely redacted in the documents, obtained under Right to Information laws.

In November the ABC reported that Barbara Nowak and Louise Cherrie — experts in aquaculture and environmental management respectively — quit the eight-person Marine Farming Planning Review Panel (MFPRP) in protest to the Storm Bay expansion approval.

The panel approved proposals by Tassal (360 hectares) and Huon Aquaculture (330 hectares) to farm new waters in Storm Bay in August.

The new documents, obtained by the Tasmanian Greens, reveal the pair resigned later the same month in a redacted letter to the Governor Kate Warner, and later wrote to Primary Industries Minister Guy Barnett explaining their reasons.

The letter they wrote has been entirely redacted, except for the first and last sentences.

The RTI officer determined the information was exempt from release because its disclosure would divulge information communicated in confidence to the Minister.

The letter was copied to seven other people.

The heavily redacted result of an RTI request submitted by the Tasmanian Greens. ( ABC News: Alexandra Humphries )

Right to Information expert Rick Snell said it could be argued not all resignation letters to ministers should be considered inherently confidential, and the significant public interest in the issue should be considered when deciding whether to release it.

In one email that was not redacted, Ms Cherrie wrote to fellow MFPRP member Heather Chong, indicating Ms Cherrie and Professor Nowak had raised concerns with panel chairman Craig Midgley before they resigned.

"We did have a few chats with Craig with some concerns, and I believe he was aware it [the resignations] was a possibility," the email said.

Tasmanian Greens MP Rosalie Woodruff said the heavily redacted RTI response said a lot, despite the lack of words.

"Two of the eight members of the Marine Farming Review Panel, Ms Louise Cherrie and Professor Barbara Nowak, marine and biosecurity experts, resigned in protest at the approval of the largest and highly controversial salmon industry expansion into Storm Bay last year," Ms Woodruff said.

"In a second letter to the Minister we understand the scientists outlined their specific concerns about the approval process and a basis for their resignation.

"Both letters have been denied to public scrutiny, despite the fact the decisions of this panel affect the functioning of the marine waterways, and the lives and livelihoods of thousands of Tasmanians."

ABC's inquiries into resignation detailed

The Right to Information documents also detail correspondence surrounding the ABC's inquiries into the resignations in November.

They show Department of Primary Industries, Parks, Water and the Environment staff were advising each other that the ABC was "ringing around" about the resignations, but some parts of those emails have been redacted.

Questions sent by the ABC to Mr Barnett's office requesting answers were also redacted because it was determined to be "internal deliberative information".

Those questions included whether Mr Barnett could confirm when he received the resignation letter, if he had sought reasons for their resignations, and if he was concerned about the abilities of the panel in the wake of the departure of the two experts.

Rick Snell said the lengthy redactions could indicate suggested answers were included. ( ABC News )

Under the RTI Act, information is "internal deliberative" and exempt from release if it consists of an opinion, advice or recommendation prepared by an officer of a public authority for deliberative processes related to the official business of a public authority or minister.

Mr Snell said due to the length of the redaction, it was possible suggested answers had been written beneath each of the questions by a department staff member.

By redacting the ABC's questions as well, information about the length of the proposed answers was also hidden, he said.

Mr Barnett said RTI decisions were made at arm's length from ministers.

"The Greens should stop trying to take a cheap shot at these hard working public servants," he said.

"I have full confidence in the Marine Farming Planning Review Panel and the advice it provides to the Government on marine farming planning matters."