Queensland's corruption watchdog says a decision by the former Newman government to retrospectively approve the bulldozing of swathes of pristine bushland may have involved maladministration.

The Crime and Corruption Commission (CCC) has referred the matter to the state's Ombudsman, saying concerns raised about the approval "could amount to corrupt conduct".

However, the CCC said there was "an absence of evidence" to support a criminal offence of improper influence.

The ABC revealed last year that mining company Melior Resources knew it did not have the required approvals when it cleared a road corridor through an area at Goondicum in central Queensland.

The bushland in question is regarded as habitat of state significance.

When questioned at the time by the ABC about the bulldozing, Melior Resources chief executive Mark McCauley said the company would seek retrospective approval. It was later granted by the Queensland Department of State Development under the former Newman government.

Mr McCauley's father Ian has been the biggest individual LNP donor of recent years, giving more than $250,000 to the party since 2009.

The McCauleys, who previously owned the mine in their own right, now hold a significant stake in Melior Resources — a publicly listed Canadian company whose sole asset is the Goondicum ilmenite mine. Ilmenite is used as a pigment in paint, plastics and paper.

Melior wanted to clear land for a new road to reduce the haulage distance to and from the mine, which sits on a cattle property owned by fifth-generation grazier Rob Campbell.

Rob and Nadia Campbell on their central Queensland property

But the company bulldozed hundreds of trees outside the authorised road corridor.

The Queensland Environment Department later told the Campbells that "unauthorised clearing and road works had been conducted... [and an] inspection also confirmed impacts to wildlife".

The department said the works had "interfered with animal breeding places and pass through areas mapped as being core koala habitat and of State Biodiversity Significance".

After Labor won power in Queensland earlier this year the Campbells wrote to the new Minister for State Development, Anthony Lynham, asking for an investigation into the retrospective approval of the bulldozing.

The Director-General of his department then referred the issue to the Crime and Corruption Commission.

In a letter sent to the Campbells this month, the CCC said it had now completed its assessment, finding that "while the concerns you have raised could amount to corrupt conduct, there is an absence of evidence to support a criminal offence related to the exercise of improper influence by the developer or any other person or a disciplinary breach providing reasonable grounds to dismiss the officers involved in the decision-making about... the development".

But in a statement to the ABC, the corruption watchdog said its "inquiries suggest decision making relating to the approval process of the land clearing may have involved maladministration".

The CCC said it had now referred its concerns to the Queensland Ombudsman, whose jurisdiction covers maladministration.

The Ombudsman's office told the ABC that confidentiality provisions in the act meant it was unable to confirm or deny if an investigation was underway.

Among the definitions of maladministration on the Ombudsman's website is administrative action that is unlawful, unreasonable, unjust, oppressive or improperly discriminatory.

The Palaszczuk Government in Queensland has vowed to push ahead with a Royal Commission-style inquiry into political donations. The probe is expected to investigate the alleged links between donations and the awarding of approvals and contracts.