Public faith in the regulation of mining in NSW was being 'severely undermined' and the minister needed to explain what was going to be done, critics say.

The NSW Ombudsman's report into the mishandling of public interest disclosures follows on from the jailing of former ministers Eddie Obeid and Ian MacDonald for cooking up crooked deals in the same Maitland office ten years ago.

The public interest disclosures which Stockton-based whistleblower Rebecca Connor and others at the Maitland mining titles office "showed or tended to show corrupt conduct", and were never properly handled or investigated, the report says.

Ms Connor's husband and former senior police officer, Allan Connor, said the serious issues his wife has raised remain outstanding.

"It is more than apparent that the department treated the NSW Ombudsman's office with contempt," Mr Connor said.

"They failed to provide documents in a timely fashion and ... documents still remain outstanding.

"The department still has not conducted a comprehensive investigation into the allegations that serious corruption committed by mining companies, mining agents and high level public servants."

Lock the Gate Alliance National Coordinator Carmel Flint said the findings were a scathing indictment of the way complaints are handled internally.

"Public faith in the regulation of mining in NSW will be severely undermined by the Ombudsman finding that the department failed to fully investigate the whistleblower disclosures or act on the deeply troubling issues raised," Ms Flint said.

"A government department that appears to lack this basic ability to transparently investigate serious internal complaints is not one that can be trusted to handle the assessment of eight new massive coal projects as the world shifts towards a renewable energy future."

Greens spokesperson for Mining, Coal and Gas, Sue Higginson said the evidence was deeply concerning, and called on the Deputy Premier and Minister for Resources Paul Toole to explain what has happened, and what he is going to do to address it.

"Findings of unreasonableness on part of government agencies dealing with resource exploitation and land use conflict are significant and not acceptable," Ms Higginson said.

"There needs to be a full open and transparent inquiry into what has happened. We now have at least two members of the community who are personally aggrieved and are carrying the burden of seeking justice and accountability in the public interest.

"Delaying the release of the Ombudsman's report is not only prolonging the denial of justice for Ms Connor, but it's further protecting corporate interests and failing to hold potentially corrupt conduct to account."

The state government's response, via the Department of Mining, Exploration and Geoscience is that it will "continue to work with the NSW Ombudsman in relation to these historic matters."

Two of the most serious allegations of corruption Ms Connor made involved proposed mines worth hundreds of million of dollars.

NEWCREST MINING complained in February 2017 that their plans to relinquish a parcel of land had been disclosed, potentially by public servants, to one of its competitors before it was made public.

That gave the other mining company a competitive advantage due to the 'first in first served' basis on which those applications were determined, says Stockton-based whistleblower Rebecca Connor says.

At the time, Newcrest's plans were not in the public domain, the Ombudsman's report has confirmed.

Details about what parcels of land mining companies would need relinquish, and when (as per their mining exploration licence requirements) were recorded in a computer-based system

"The mining companies had greater access to that than I did," Ms Connor said. "And I was the title's manager. So, the mining agents (who work for the mining companies) would ring up and get reports, and they would generate reports and email them to certain agents saying, this land's due to come up soon."

Newcrest mining was due to provide relinquish 50 per cent of its land. On the day that submission was due, a competitor applied to take up those precise parcels of land.

However, unbeknownst to the competitor and anyone else outside the discussion, Newcrest had been given a week's reprieve, delaying the process for seven days.

"So Newcrest goes, hang on a minute, how would they know that? Not only that, they knew exactly which units of land, because you could have 15, 20, 30 units on this one parcel of land."

The explanation offered was that Newcrest's competitor had "guessed" which units were coming up, Ms Connor said.

"But when it came back to me and I had a look, I just went, no, that's not the case. Have a look at the units. They are all over the place ... they pop out all over the place."

While an internal investigation was initiated, the relevant governance team got broken up, and the whole thing "just fell over", Ms Connor said, and it was "never looked at again".

The Ombudsman has confirmed Ms Connor's story. The investigation which was supposed to take place, after an initial document management systems review, never happened.

"There is also no information about such inquiries in the final investigation report... and no records explaining why DRG decided not to interview the staff members or pursue the investigation further," the report says.

It went to ICAC on the basis of reasonable suspicion of corrupt conduct, then was sent back to DRG to investigate, with instructions to produce and share a copy of the investigation report.

That investigation, which included evidence from internal systems experts corroborating Ms Connor's view, took a strange turn.

Despite the experts' evidence, the investigator, whose name is redacted in the copy of the report issued to Ms Connor, referred the evidence given by the mining agent, the Ombudsman's report says.

That conclusion was based on an unsubstantiated claim from the competitor and was "difficult to understand," the Ombudsman said.

SHENHUA WATERMARK'S proposal to mine land near Gunnedah on the Liverpool Plains was another case which Ms Connor says was mishandled.

The massive thermal and coking coal mine attracted fierce opposition, including from local farmers who wanted to protect the region's fertile black soil.

One of the conditions on Shenhua's licence was that they had to build a mine within five years, which they didn't, Ms Connor told the Newcastle Herald.

"They were negotiating to have that condition, 46B, amended," Ms Connor said.

"At that time the 'top end of the department' was negotiating to give them back $350 million to get them to relinquish some of that land because it was sensitive farmland.

"I told them they didn't have to buy it back because they hadn't met the conditions of their mining licence. So they had to relinquish it - you just call it in. Not pay them $350 million.

"And then suddenly we've got an election going on ... and I get phone calls and text messages telling me no one is to mention the word Shenhua Watermark leading up to the election.

"They pulled it off the system. I had staff coming to me going, it's gone. We were working on this condition 46, but it's gone. It's not in the system. I was told: 'It can't exist, can't be mentioned, and you are not to have any involvement.

"I was like, this blows my mind, actually. It was at least two months later that they rang me and said, what's going on with that condition 46B for Shenhua Watermark? So for about four months, that lease, worth billions of dollars, didn't exist. I don't know what happened in the end ... I was gone by then."

The state government has since paid the Chinese-owned mining company $100 million to withdraw from its Watermark coal mine.