Environmental activists have accused Whitehaven Coal of clearing land illegally at their Maules Creek mine in northwest NSW.
The mine's biodiversity plan prohibits Whitehaven from clearing land when the temperature exceeds 35 degrees to give animals the best chance of survival in the clearance zones.
Activists say clearing above this temperature kills more animals as they tend to retreat to trees to stay cool.
However, the Leard Forest Alliance says the mine continued clearing land hours after residents recorded 35C temperatures.
Whitehaven Coal executive general manager of operations Jamie Frankcombe denies the claims.
"Onsite automatic weather stations send a series of automated text messages to the clearing team as the temperature approaches 35 degrees," he said.
"When the temperature reaches 35C clearing ceases, and this is exactly what occurred."
Leard Forest Alliance spokesman Phil Spark said the mine's onsite weather station couldn't be trusted.
"We are calling for independent monitoring of when clearing can occur," he said.
"There is zero faith in Whitehaven being able to self-regulate, and today's findings are an example of Whitehaven's disregard of regulations and their anxiousness to cut corners in a crashing coal market."
The Bureau of Meteorology's closest measuring station to the mine, roughly 35km away, recorded a temperature of 35 degrees just over an hour before clearing stopped.