The announcement comes after the Land and Environment Court ruled that Rio Tinto subsidiary Coal & Allied’s proposed expansion of its Warkworth mine should not proceed despite gaining approval by the Planning Assessment Commission.

The latest move by minister Hazzard is seen as trying to avoid future legal challenges to the Drayton South development if it is approved.

Hazzard has written to the independent PAC requesting that it defer its review of the proposed open-cut mine to allow the Department of Planning and Infrastructure to undertake further work on concerns raised in public submissions.

Public hearings for the project were due to start in June.

“The department is currently in the process of reviewing the submissions received during the project’s public exhibition late last year, including detailed submissions from both the Coolmore and Darley studs,” Hazzard said.

“I’ve written to the acting chair of the PAC stating that the department is concerned the proposal does not adequately address impacts on the studs.

“To ensure a thorough review of all issues can take place, I’ve asked the PAC to postpone its review of the project.

“Once the department has considered the response from the mining company, I will be in a position to advise the PAC how to proceed further.”

Hazzard said the adjacent horse studs formed part of the Upper Hunter’s Equine Critical Industry Cluster (CIC), as identified in the Government’s Strategic Regional Land Use Policy.

The region’s thoroughbred industry is one of two CICs identified for heightened protection from mining and other resources activities, along with the winemaking industry.

The NSW government is seeking to mitigate the impact of investment in the state’s mining industry after the Land and Environment Court ruling against the Warkworth expansion and Boral’s Berrima Medway colliery extension projects.

Hazzard has joined Coal & Allied in appealing the court’s decision to knock back the Warkworth expansion, which it had received the planning department’s director-general approval.

A statement from the Department of Planning states: “The original decision in the Land and Environment court may have implications that are broader than this particular development, in particular for the assessment of other mining projects.”

Rio Tinto has warned of further job losses at its Mt Thorley Warkworth coal mine, despite the Supreme Court’s decision to expedite the company’s appeal against the barring of an expansion of the operation.

The Land and Environment Court last month overturned the development consent received in 2012, based on an appeal initiated by the Bulga-Milbrodale Progress Association.

The matters will now be heard on July 30 to August 1.