METGASCO did not tell a parliamentary inquiry the company was disposing of coal seam gas wastewater at the Casino sewage treatment plant.
The Northern Star on June 13, revealed the company disposed of more than 1.3 million litres at the plant in the 10 months to March.
The company was told to stop the disposal after it was found to be in breach of the Richmond Valley Council's licence to operate the plant.
But Metgasco chief operating officer Michael O'Brien made no mention of the disposal when giving evidence to the NSW Government inquiry into coal seam gas on December 8.
Under questioning from Greens MLC Jeremy Buckingham, Mr O'Brien explained the company disposed of water in "above-ground holding ponds".
"The only way you deal with produced water and drilling fluids is to hold them in these ponds?" Mr Buckingham asked.
Mr O'Brien responded: "Currently, for our production pilots, that is the case, but when we go into production we will look for a beneficial use for the water."
Metgasco CEO Peter Henderson said Mr O'Brien's response "was based on long-term disposal of the pond water, that is after being stored in the holding ponds".
"In this sense the answer was correct, we currently don't have approval for specific long-term beneficial uses," he said.
But that failed to satisfy Mr Buckingham, who will refer the matter to a parliamentary committee.
"I believe it is a very serious matter that the disposal of produced water at the Casino sewage treatment plant was not disclosed," Mr Buckingham said.
"We believe it was disingenuous at best and deliberately misleading at worst.
"In terms of the position of Metgasco, I believe they are just more weasel words from a company that has lost the faith of the community."