The NSW premier has brushed off opposition claims that the public has been misled by an environmental body on coal dust air pollution in the Hunter Valley.

Opposition environment spokesman Luke Foley says documents released through freedom of information reveal the Environmental Protection Authority (EPA) falsely claimed there were not elevated levels of air pollution from coal train wagons.

Mr Foley says the EPA “covered up crucial facts” about the pollution in the Hunter Valley rail corridor.

However, Premier Barry O’Farrell has dismissed the claims.

“Well, I won’t say which orifice he’s talking out of,” he told reporters on Sunday.

The fact was the Australian Rail Track Corporation (ARTC), a federal entity, had produced two reports that had differing results, the premier said.

“The EPA and the Office of the Environment and Heritage have sent that to a third party to see which was correct, and that work’s currently being done,” he said.

“But no one has ever denied that the movement of trains on rail lines where coal is being moved, that we don’t get particulate and dust matters are produced.”

The opposition claimed a government-led review of ARTC’s reports on air particle pollution highlighted spikes in pollution as coal trains passed through the area.

But Environment Minister Robyn Parker stated otherwise, Mr Foley claimed.

“If the Minister has unknowingly misled the parliament, as a result of false advice from the EPA leadership, she must correct the record immediately,” he said.

A statement from the environment minister’s office stated all of the minister’s statements had been made on the basis of the best available evidence and science.