The NSW government has confirmed it is conducting an investigation into the Australian subsidiary of South Korean giant KEPCO that could affect the company's plans for a $1.5 billion coal mine in the Bylong Valley.

Lee Shearer, the state's resources regulator, told estimates on Friday that the government had begun investigations into "a number of mining title holders, KEPCO being one".

Korean-owned KEPCO wants to develop a coal mine in the Bylong Valley. Credit:Brendan Esposito

A Planning department spokeswoman confirmed on Monday the investigation involved "allegations of corruption and bribery by its parent company, KEPCO Electric Power Corp in South Korea, and other subsidiaries".

Adam Searle, Labor's mining spokesman who had pressed Ms Shearer on the probes, said the Korean utility had been the focus of well-publicised scandals, including the fabrication of safety tests for nuclear equipment.