The parliamentary committee scrutinising the Morrison government’s handling of the pandemic will demand a trove of secret documents after an extraordinary judgment finding national cabinet records can be accessed under the freedom of information regime.

The first-of-its-kind case in the Administrative Appeals Tribunal was brought by Senate crossbencher Rex Patrick, who argued the prime minister had no grounds to extend cabinet confidentiality to his national cabinet meetings with state premiers and chief ministers.

Justice Richard White agreed, finding the national cabinet was not, as the prime minister had contended, a subcommittee of the federal cabinet.

White concluded none of the documents sought by Patrick under FoI were an “official record of a committee of cabinet” and were, therefore, not covered by the cabinet exemption.

Katy Gallagher, the shadow finance minister and chair of the Senate select committee on Covid-19, told Guardian Australia she would move for immediate disclosure of key documents outlining the pandemic response.

“This is a devastating judgment for the prime minister, who was the architect of a structure specifically designed to avoid transparency and to refuse access to information that is genuinely in the public interest,” Gallagher said.

“We have a long list of documents that have been kept secret under the so-called national cabinet defence that will be re-lodged and in light of this judgment we expect all the documents and information to be released immediately.”