A multinational uranium miner persuaded the federal government to drop a requirement forcing it to show that a mine in outback Western Australia would not make any species extinct before it could go ahead.

Canadian-based Cameco argued in November 2017 the condition proposed by the government for the Yeelirrie uranium mine, in goldfields north of Kalgoorlie, would be too difficult to meet.

The mine was approved on 10 April, the day before the federal election was called, with a different set of conditions relating to protecting species.

Environmental groups say the approval was politically timed and at odds with a 2016 recommendation by the WA Environmental Protection Authority that the mine be blocked due to the risk to about 140 subterranean stygofauna and troglofauna species – tiny animals that live in groundwater and air pockets above the water table.

A Cameco presentation to the department, released to the Greens through Senate estimates, shows the government proposed approving the mine with a condition the company must first demonstrate that no species would be made extinct during the works.

Cameco Australia said this did not recognise “inherent difficulties associated with sampling for and describing species”, including the inadequacy of techniques to sample microscopic species that live underground and challenges in determining whether animals were of the same species. It said the condition was “not realistic and unlikely to be achieved – ever”.

The condition did not appear in the final approval signed by the environment minister, Melissa Price, which was made public after being posted on the environment department’s website on 24 April.

Instead, the government said the company should develop a groundwater management program, limit groundwater extraction in some places to 50cm and have evidence from a qualified ecologist that work in part of the area affected by the mine would not lead to extinction. All would need to be submitted to the environment minister for approval.

Mia Pepper, from the Conservation Council of WA, said the change to the conditions showed mining companies had a disproportionate influence in what was a flawed environmental approvals process.

She said a clear condition to stop extinction had been replaced with convoluted requirements that shifted the onus for stopping species loss from the company to the government.

“I think the public and government department should expect [that] companies can provide evidence that species won’t be made extinct,” she said. “The attitude in the mining industry around subterranean fauna has been pretty poor. Whether they are tiny species or cute and cuddly species, they should all be protected. Who are we to decide?”

Pepper said Yeelirrie had been subject to probably the most extensive subterranean fauna survey at an Australian mine site when it was owned by BHP Billiton. “The chances that these species exist elsewhere is almost zero to none. That is backed up by the BHP survey and the EPA,” she said.

The Cameco Australia general manager, Simon Williamson, said the company’s presentation to the department was a normal part of the approval process under the Environment Protection and Biodiversity Conservation Act, and disputed the assertion that the final conditions shifted the onus to protect the species on to the government.

“We now have a significant requirement to manage groundwater extraction in a way that will significantly reduce impact on these species,” he said.

Pepper and Williamson agreed most microscopic subterranean species at the mine site were unlikely to be found anywhere else. But Williamson said the initial condition was problematic, as there was a legal issue in asking a developer to prove a negative statement and it was impossible to sample every microscopic underground species on site.

“How can we demonstrate in advance that we won’t make these species extinct? It’s trying to prove a double negative,” he said. “The condition they started with, I think, was unworkable. This is common sense and a better outcome for the environment. What we have now is direct preservation of the habitat where those species have been found.”

The future of the commonwealth environment legislation is under question: the Coalition says it would retain it, while Labor says it would introduce a new law and a national environment protection authority.

The Labor commitment, which has not been fleshed out, followed an internal campaign by the Labor Environment Action Network that won support from nearly 500 local party branches and coincided with a joint green movement push.

A government spokesman said the Yeelirrie project had been approved subject to 32 strict conditions to avoid and mitigate potential environmental impacts. He said it had triggered a “whole-of-environment” assessment such that all impacts were considered, not just those to issues of national environmental significance.

“With the conditions in place, the minister is satisfied that risks to the environment will be appropriately managed and balanced against the social and economic benefits of the project,” the spokesman said.

Labor has called on Price to explain why the mine was approved in the shadow of an election campaign.

Williamson welcomed the approval but said a decision to advance the Yeelirrie mine would depend on market conditions, which were currently challenging. The mine is also the subject of a legal challenge in the WA court of appeal by the conservation council and three Tjiwarl traditional owners.