The existing approvals only allow production from the open cut MTW operations in the Hunter Valley until late 2015 – a key concern for Rio Tinto Coal Australia managing director Chris Salisbury.

"We're now running out of time in what is an extremely challenging environment for the coal industry, where mines without a strong future are being shut down," he told the Newcastle Herald in the last week of June.

Yet RTCA’s ability to produce lengthy environmental impact statements for each mine in just three-and-a-half weeks from receiving the government’s assessment requirements has come under question.

“Shoebridge said whistleblowers told him Rio was ‘basically ready to go to the printers’ as soon as the miner received the requirements for its Warkworth and Mount Thorley continuation projects from the Director-General of Planning on May 22,” the Sydney Morning Herald reported.

“Rio submitted its response on June 15 in the form of two 400-plus page environmental impact reports along with 33 attached consultants' reports running into the thousands of pages.

“Shoebridge said the miner could only have produced the mountain of reports ‘if they had been at the table while the rules were being set by the Department of Planning’.”

The politician subsequently said it was “regulatory capture of the worst kind”

"The Director-General's requirements are meant to protect the state's social, environmental and economic interests,” he reportedly said.

“They are not meant to be workshopped with miners to ensure a damaging mining project is approved."

A Planning Department spokesman reportedly rejected claims that any special working group had been formed with Rio.

"[Department] staff join other relevant NSW government agencies to meet with the proponents of every major mining proposal to answer questions about government policy and clarify expectations about the assessment of key environmental issues," he told the newspaper.

"This is normal practice and benefits the community and stakeholders by ensuring, as much as possible, that these processes do not drag on for years."

An RTCA spokesman said the company followed due process at all times.

He further said RTCA "made no secret of the fact that we are seeking to have our planning applications approved as quickly as possible through the appropriate processes, to secure the future of Mount Thorley Warkworth and the jobs of the 1300 people who work there".

Bulga Milbrodale Progress Association president John Krey reportedly claimed that RTCA wanted to unlock the potential of another 150 million tonnes of coal so it could “sell” the MTW operations.

"There's a big incentive, that's why they are trying to crash through the process," Krey told the newspaper.

In its continuation projects, RTCA aims to maintain existing production rates of 18 million tonnes per annum run of mine from the Warkworth mine and 10Mtpa ROM from Mount Thorley.

While the NSW Supreme Court upheld a Land and Environment Court decision to halt the extension plans in April, the state government had since passed a planning policy that made the economic benefits the "primary consideration".

RTCA claims the extension projects have net economic benefits of $1.5 billion and royalties of $617 million.