A dispute between the ministers which has been ongoing for a year has intensified as the heaviest rain since 1961 batters the Nepean and Hawkesbury catchment and Sydney’s main dam spills over.

Mr Elliott said he had been on the public record in his role as the MP for Baulkham Hills about the need to release water from the dam in preparation for the La Nina weather event.

He said on Sunday said there would need to be “a full and frank discussion” about managing dam levels once the severe weather event was over. Ms Pavey said the significant rainfall caused the spill.

“It’s naive to think we could have reduced the dam to 25 per cent which is the number on current projections that would have avoided a spill,” Ms Pavey said.

“We’ve never had the dam below 38 per cent and this is a one-in-50-year event.”

The government is working on changing the operating licence of WaterNSW, the agency responsible for the dam, to allow it to release water to keep the dam at 95 per cent capacity.

A spokesman for the agency said: “WaterNSW confirms that 130 gigalitres of water has been released in recent months to hold the storage at around 1m below full supply level.

“This was done in accordance with strict operating protocols and resulted in the need for dam releases during this event being delayed by a full day, allowing greater time for preparedness.”

Since the heavy rain hit, Warragamba’s spillway has released 450 gigalitres a day. Sydney Harbour holds about 500 gigalitres.

Premier Gladys Berejiklian said it was not feasible to reduce the dam to 25 per cent capacity.

“You have to look beyond the dam; it’s all the rivers that are overflowing, it’s the sustained rainfall in very short periods of time,” Ms Berejiklian said.

Mr Elliott has told colleagues that Ms Pavey’s reluctance to reduce levels was because she was worried about the perception of wasting water rather than protecting Sydney homes from flooding.

A senior government source said Mr Elliott was “absolutely furious” at Ms Pavey and had been raising the issue with her in cabinet for many months.

The issue of the dam levels and Sydney’s water restrictions were a source of contention in cabinet last year, with Treasurer Dominic Perrottet a vocal opponent of retaining the restrictions.

The government wound back Sydney’s water restrictions to level 1 in February last year when the dam reached 80 per cent capacity but the restrictions stayed in place until December last year.

Meanwhile, the Deputy Premier John Barilaro said regional NSW was bracing for more economic devastation after parts of the Mid North Coast were hit with the worst floods in 100 years.

Mr Barilaro said it was heartbreaking to see regional NSW hit once again as it began to recover from the devastating bushfires and COVID-19 economic crisis.

“It is hard to believe that just as the regions were finding their feet after drought, bushfires and COVID-19 they are slammed once more, this time with floods,” Mr Barilaro said.

“The economic impact these disasters are having on the livelihood of our regional communities is devastating and, whilst people in the bush are resilient, it’s heart-wrenching for local businesses to have to rebuild once more,” he said.