Opponents of a new dam in NSW say it will cost several times more than the benefit it brings. 

NSW Greens MP Cate Faehrmann says a summary of the business case for the proposed Dungowan Dam near Tamworth shows the dam would only produce 27 cents of benefit for every dollar invested.

The NSW Government has refused to publicly release the document.

“The business case that the government has produced just shows it doesn't stack up,” she said.

“They cannot show there is enough benefit to the community to justify what is going to be upwards of $1.3 billion.”

The cost of the dam has almost tripled from $484 million when it was first announced at the height of the last drought in 2019.

The previous federal government pledged to pick up half the bill, but the new Labor government has not yet announced a position.

NSW Water Minister and Member for Tamworth Kevin Anderson says it is impossible to put a price on water security for Tamworth and the wider region.

“The summary business case clearly shows that this city would run out of water again if we would go back to a 2019-2020 drought,” he said.

“They're putting a cost on that, and I think back to 2019 when we were on level-five water restrictions.

“I think it's disgraceful.”

He also responded to claims that the dam was selected to benefit irrigators, rather than for human needs.

“This rubbish that this dam is for irrigators only is exactly that,” he said.

“It clearly says it needs water for the city, it needs water for agriculture and it needs water for industry.”

Ms Faehrmann says she will continue to push for the release of the full business case.