The National Party wants an urgent overhaul of the New South Wales Independent Planning Commission (IPC), as Deputy Premier John Barilaro forges ahead with his goal of making the state Australia's top mining investment destination.

Key points: Nationals MPs want changes to the planning commission to give foreign investors certainty over the approvals process for major developments

Nationals MPs want changes to the planning commission to give foreign investors certainty over the approvals process for major developments The calls come in response to the rejection of a proposed multi-million-dollar Bylong Valley coal mine

The calls come in response to the rejection of a proposed multi-million-dollar Bylong Valley coal mine The independent commission was brought in last year in the wake of corruption under the former Labor government

The party says without changes, the Government will be forced to "tax the hell out of people", with foreign investors having no certainty in the planning process on major developments.

South Korean company Kepco spent $700 million buying and developing land for its proposed Bylong Valley coal mine in the state's central west, only for it to be refused by the IPC.

Now, Mr Barilaro said he feared potential investors would not pursue projects in NSW unless changes were made.

"Uncertainty around the IPC's decision-making process is creating a sovereign risk for mining investment in NSW," he said.

"There is a lack of consistency, a lack of certainty, and the length of time taken to reach some of these decisions is unacceptable.

"Potential investors don't have to pursue projects in NSW, and unless there are changes to the IPC, the concern is that many will choose not to."

The local mayor says the transparency of the IPC is far greater than "a decision made by a minister behind closed doors". ( ABC Upper Hunter: Eliza Goetze )

There has also been criticism from the NSW Minerals Council, which has launched a public campaign calling on the State Government to act.

"The IPC now seems to be setting its own policy agenda, ignoring the policy settings of the elected government of the day," chief executive Stephen Galilee said.

"It's ignoring the assessment recommendations of the Department of Planning itself, and making determinations based on a different set of circumstances other than the priorities of the elected governments.

"That's creating uncertainty for our sector."

The IPC was brought in last year to replace the Planning Assessment Committee in the wake of Labor Party corruption, operating independently of the government.

There was strong local opposition to the mine proposal. ( Supplied )

Bylong mine decision a tipping point

Michael Johnsen, the Nationals Member for the Upper Hunter, said an independent body had a place in the decision-making process but that a significant review was needed.

"I think that's only fair and reasonable, but they should be an advisory body, not a decision-making body," he said.

"We can't have an independent body turn around and basically go against all the recommendations and all the experts. That's wrong. It can't happen."

The Bylong Valley decision is seemingly the tipping point for those calling for change.

"I actually want to see the State Government, through cabinet, take back control of the decision making with state-significant developments," Mr Johnsen said.

"The state's own major infrastructure projects don't go through the process — if it's good enough for the private sector, why not give it to the public sector as well?"

"If we've got some levels of falling revenue, we've got two choices to make it up: we can tax the hell out of people, or we can bring back some confidence into the international investment market and invest and create jobs and income in NSW."

Graham 'Tag' Tanner spent eight years lobbying against the mine project, which neighbours his property. ( ABC Upper Hunter: Amelia Bernasconi )

But Martin Rush, the Mayor of Muswellbrook Shire, which is the largest producer of coal in the state, was quick to remind the Government that it established the IPC.

"They set the system up and said, 'This will be great, it'll take the political decision making out of the process and make it a fair process, it'll take the politics out'," Cr Rush, a former ALP candidate, said.

"Then when they get a decision they don't like, they attack it.

"I think the IPC, broadly speaking, could be better resourced, but it is certainly doing the job that they need to do."

While Kepco could challenge the Bylong Valley judgment in court, the Government is unlikely to step in.

"It doesn't have the power to overturn this particular decision without making retrospective changes to legislation, and there's no appetite to do that," Mr Johnsen said.

"I wouldn't recommend the Government make retrospective changes; that's always a bit of a dangerous thing to do."