The New South Wales Attorney General has become a defendant in a case that is trying to shut down a corruption inquiry into coal licenses.

Mining magnate Travers Duncan is trying to shut down an Independent Commission Against Corruption (ICAC) inquiry into the Mount Penny coal licence and stop the ICAC Commissioner making any findings on it.

He is one of seven investors whose company Cascade Coal allegedly won a rigged tender that covered properties owned by former NSW Labor Minster Eddie Obeid and his associates.

The Supreme Court has heard that the NSW Attorney General has become the third defendant in the case along with the ICAC and its Commissioner, David Ipp.

The public gallery is full and people are also standing in the corridor to try to hear what is being said in court.