NSW public servants are attempting to keep a lid on documents about classification of the Adler A-110 shotgun.

Bureaucrats would have their ability to offer frank and fearless advice curtailed if police documents relating to the reclassification of the Adler A-110 shotgun were released to the public, a tribunal has heard.

More than a year after Adler’s classification was updated by the Council of Australian Governments, NSW police are fighting to prevent the release of the documents which could embarrass state minister Troy Grant if they reveal that his advocacy for a less restrictive classification was at odds with his department’s advice.

Georgina Gold, the general manager of operations at the NSW Police Force Firearms Registry, was called before a NSW Civil and Administrative Appeals Tribunal on Tuesday by police lawyers seeking to defeat an application by Greens MP David Shoebridge to release the police memorandums and advice. Also a member of the COAG sub-committee tasked with reviewing the National Firearms Agreement and Adler classification, Gold said it was “human nature” for bureaucrats to be concerned about giving frank advice if they knew it could end up on the front page of a newspaper and cause “difficulties” for the government.

Gold revealed that as the Adler debate first took off in 2015, the sub-committee of state and commonwealth staff working on the issue was subject to a clamp-down by the federal Attorney-General’s office after details from a meeting were leaked to the press. In an attempt to prevent future disclosures, members of the group were given as little as a day to receive and respond to papers being circulated which included subtle but significant proposed changes. The incident was put forward as an example of the damage that releasing information could have on government processes.

Shoebridge, who is representing himself, argued in cross-examination that an illegal leak to the press was not the same as an information request submitted under NSW law. He also noted that jurisdictions including WA, the ACT, and the NT had not objected to releasing the materials requested, though others had.

In a case that hinges on questions of transparency, the state government’s lawyers have so far refused to allow submissions and affidavits before the Tribunal to be publicly released. At the Tuesday hearing, Crown Solicitor Helen Sims foreshadowed that the state would attempt to use cabinet-in-confidence exemptions to quash the release of the documents.

The fight to hold back the briefings and opinions comes after COAG agreed to classify the five-shot version of the Adler as a Category B weapon and the seven-shot version as a Category D weapon in December 2016, effectively ending the long-running political stoush between gun control advocates and shooters in a draw.

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NSW Police Minister Troy Grant had publicly called for both versions of the gun to be put in the less-restrictive Category B but an earlier freedom of information request by Shoebridge revealed that NSW Police had advised the Minister of public safety concerns around the Adler A-110 relating to its rapid rate of fire. The police advice was at odds with Grant’s position and compared the Adler to pump action shotguns which are heavily restricted and classified as Category C firearms.

The case will continue in February 2018.