Laws that make land clearing in New South Wales easier have been ruled invalid by the NSW land and environment court after a challenge filed by the Nature Conservation Council.

In November 2016, the NSW Coalition government scrapped the state’s Native Vegetation Act, the Threatened Species Conservation Act and the Nature Conservation Trust Act, and replaced them with its new Biodiversity Conservation Act.

The government also introduced a suite of codes that exempted clearing in a range of circumstances from normal development assessment requirements.

The council, represented by the environmental defenders office NSW, argued in court in Sydney on Friday that the codes were invalid because the environment minister had not approved them before they were implemented.

The council’s case was backed by the court, and the NSW government now has the option to reintroduce the codes with the appropriate oversight.

The council’s chief executive, Kate Smolski, urged the government not to do that.

“It would be completely cynical for the government to immediately remake these laws without first correcting their many flaws and including environmental protections the community wants and the science says we need,” she said.

Crucially, among the law changes, the government introduced a suite of self-assessible codes, which allowed farmers to decide whether or not a piece of land could be cleared of trees and shrubs. Some of those codes had no requirements for offsets, leading experts to fear that clearing rates could double in some parts of NSW.

Such codes have been central to the surge in land clearing in Queensland, after the former LNP government introduced them in 2012.

“By the government’s own assessment, they will lead to a spike in clearing of up to 45% and expose threatened wildlife habitat to destruction, including 99% of identified koala habitat on private land,” Smolski said.

Since the codes that exempt clearing form normal development assessment procedures could have a significant impact on the environment, they required the environment minister, Gabrielle Upton, to approve them before they were implemented by primary industries minister, Niall Blair.

That never happened.

Since the codes do not require an act of parliament, they could be reintroduced almost immediately, as long as Upton approves them before they are implemented.

David Morris, the chief executive of the environmental defenders’ office NSW, told Guardian Australia the ruling technically made any land clearing that has occurred under the codes unlawful. And any new clearing will require a full development assessment until new codes are introduced.

“This is a legal and policy low point for NSW,” he said.

“In conceding that they failed to follow due process, the government gives the strong impression of making laws on the run.

“This is not simply a matter of incorrect paperwork. Ecologically sustainable development is not just another box to tick. The environment minister has a legal responsibility to protect biodiversity in this state.

“Land clearing is a major threat to biodiversity, as habitat for many animals and birds is wiped out, along with thousands of hectares of native vegetation.”