The federal government has until now tried to stand tough. NSW Premier Mike Baird, who signed off on the Shenhua project in January, spoke in support of the mine at the farmers conference. On Wednesday. Prime Minister Tony Abbott lent his support on another Sydney radio program.

"All the signs tell us it is not going to have an impact on the water table and frankly if it is not going to damage the farming areas. I think we should say let's go with it," Mr Abbott said.

Mr Hunt adopted a different tone on Thursday, suggesting that previous media reporting of the approval under the Environmental Protection and Biodiversity Act which he granted last week had not made it sufficiently clear that approval of a water management plan was still a significant hurdle.

"It was a conditional approval," Mr Hunt said. "Today I am making the point that I will not proceed or approve the final plan unless and until the IESC is fully satisfied."

Mr Hunt's office said it was always intended that he would sign off on Shenhua's water management plans and it was only logical he would take scientific advice. They denied Mr Hunt had been bullied by Mr Jones.

Shenhua, which paid $300 million in 2008 to buy an exploration licence for the area and has been struggling to win approval for four years, said it was not rattled by the apparent change in Mr Hunt's approach and it was confident it would be able to produce a management plan that would satisfy the scientific committee and Mr Hunt.

"Shenhua has never shied from scrutiny and genuine scientific review of the assessments supporting the Watermark project, which have been validated at every stage of the process. The minister and the IESC have both confirmed impacts on groundwater will be negligible and can be managed during operations with strict conditions," project manager Paul Jackson said.

Jon-Maree Baker, executive officer of Namoi Water, which represents water users in the catchment around the mine, said redrafting the management plan would not guarantee the aquifer was protected, and the mine should be stopped.


She was concerned that the NSW government, which regulates water usage, would lack the resources to monitor Shenhua's impact on aquifers. She said the risk for farmers was that the water management plan would just be paper shuffling.

She said it would be hard for farmers to prove that the company had breached the conditions of approval. "Once the project is approved, the onus is on the local farmer to prove that a multinational coal mine is breaking the rules," she said.

The water management plan involves the monitoring and technical arrangements to ensure Shenhua is complying with a pledge to curb the mine's impact on ground water. After that, the final step will be for the NSW government to allow Shenhua to convert its exploration licence into a full mining licence. This is usually a formality.

Shenhua argues that the mine's location on the ridge country known as Mount Watermark will minimise the impact on the surrounding black soil agricultural lands and their aquifers, especially the upper Namoi catchment that feeds the region.

The scientific committee's report to Mr Hunt last month said it was considered "unlikely" that groundwater drawdown would extend beyond Shenhua's estimates. It said the company's modelling was "sufficiently robust to draw conclusions as to the most likely impacts".

But it went on to say that "If the proposed project is approved, additional monitoring and finer-scale groundwater modelling should be undertaken as mining progresses to improve confidence in predictions and support."

The company has been asked to install new monitoring equipment and identify exactly what water readings in specific locations will trigger an order to cease work on the mine.