The recently completed feasibility study found the Dungowan upgrade would cost $480 million, more than three times the combined allocation of $150 million.

There are fears the federal government will withdraw its $75m if the state government doesn’t spend it soon.

NSW Nationals leader John Barilaro insisted the state government was still prepared to hold up its end of the bargain, as long as the federal government allowed the money to be spent on an alternative project that achieved the same result.

“It could be Chaffey, it could be Dungowan, it could be something else entirely new that we haven’t even spoke about,” Mr Barilaro said.

“If you can get the same outcome in relation to the amount of water by doing more work at Chaffey, for what could possibly be one third of the price or half the price, why wouldn’t you?

“Whatever it is, let’s make sure we spend the money wisely, because it is limited and we want to get maximum bang for our buck. 

“I want to see some flexibility from the feds, we’ll show flexibility from the state perspective, and get it done.”

Mr Barilaro knocked back suggestions of a cost blow out and said the purpose of the feasibility study was to identify the true cost of the project.

Tamworth Regional Council’s water director Bruce Logan said based on Dungowan Dam’s $480m-price tag, other options had to be investigated to see if they could provide a similar level of water security at a lower cost.

“Of course we would also like to see the $75 million originally allocated to the Dungowan Dam project by the Australian government used to fund further investigation and fund the preferred option, whatever that may be,” Mr Logan said.

Council’s modelling shows the recent Chaffey Dam upgrade gives Tamworth enough water to support its growth for the next 20 to 30 years.