Speaking at a dinner on Monday night at the NSW Minerals Council's flagship annual conference at the Crowne Plaza Hunter Valley, Mr Barilaro accused the commission of "extraordinary over-reach" in saying it was thinking about putting emissions-related export restrictions on a Hunter coal mine.

He did so knowing Dr O'Kane was speaking at the conference the following morning.

Despite strong expectations she would respond to the criticisms, Ms O'Kane instead delivered a speech titled "addressing major problems in mining" and declined to speak or answer questions about the issue, saying it would be against commission policy.

And when Planning Minister Rob Stokes was contacted for comment, he said Dr O'Kane had his full support in leading the commission.

"NSW has a robust system that provides expertise, transparency and independence when determining major projects that have long-lasting impacts for future generations," Mr Stokes said.

As reported in Monday's Newcastle Herald, the commission is considering imposing a condition on the United Wambo open-cut near Singleton that would force it to restrict its sales to those countries who had signed the Paris agreement, or who had what the secretary of the NSW planning department considered were "similar policies".

The condition has been welcomed by environmental groups including Greenpeace and Lock The Gate, but it has angered the coal industry and some state and federal Coalition MPs, who are also concerned about the commission wanting United Wambo to have responsibility for so-called "Scope 3" carbon emissions.

In coal mining, Scope 1 emissions are those gases released by the coal when mined. Scope 2 emissions are those associated with the mining - such as electricity and diesel - while Scope 3 emissions come from the burning of the coal.

Mr Barilaro said that under this internationally recognised standard, the carbon emissions were counted by the nation buying Australia's export coal.

To do anything else was to "double count" the emissions, because Scope 3 emissions from Australia export mines were properly accounted for as the Scope 1 emissions of overseas power stations.

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"Seeing the IPC reference Scope 3 as a genuine reason to reject or influence mining decisions, resource decisions, planning decisions is something we as a government must react to immediately and urgently," Mr Barilaro said to strong applause from his 500-strong audience on Monday night.

Mr Barilaro said the planning system in NSW was a "black box", with an un-elected and "so-called" independent body turning out decisions that were "out of kilter" with the objectives of the government.

NSW Minerals Council chief executive Stephen Galilee also criticised the commission, saying "we support the deputy premier's determination to ensure the NSW government, and not an un-elected body, sets policy in the way that projects are assessed and emissions accounted for in that process".

He said the onus was on the government to "make changes to the assessment process" to address the concerns expressed by Mr Barilaro and shared by the coal industry.

"We want the government to reform the Independent Planning Commission to make it more accountable to the government in relation to the decisions that it makes," Mr Galilee said.

"At the moment no-one seems to be accountable for the decisions and determinations that are made. The government doesn't take responsibility for them and the commission isn't able to explain them until they're made.

"That's why there's a lack of confidence across the industry in the determinations, outcomes and processes we are going through."

Lock The Gate spokesperson Georgina Woods criticised Mr Barilaro's "double counting" argument, saying "it's not counting of any kind". She said UN accounting rules and the consideration of "downstream emissions" in mining approvals were different things that should not be "mashed together".

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