Former Greens leader Bob Brown has called on the major political parties to be upfront about their position on the raising of the wall of Sydney's Warragamba Dam ahead of the federal election.

The NSW government plan to raise the wall 14 metres will be subject to federal government approval after the environmental impact statement is released later this year and the final business case is considered.

The project came under scrutiny after AAP revealed in March the Berejiklian government was actually planning to raise each end of the wall – the dam abutments – by 17m so it could easily be modified in the future to hold back additional water.

Critics say the plan puts at risk threatened flora and fauna that could be inundated by dammed water in the world heritage-listed Blue Mountains.

Dr Brown called on the coalition, Labor and all other parties to be upfront about their position before voters head to the polls on May 18.

“The whole lot should declare the hand the Greens have on protecting the Blue Mountains heritage area,” he told AAP on Saturday.

“The leaders of the parties should be very clear about what they think about it.”

The veteran environmental activist is critical of the plan which he says “doesn’t make sense” and has questioned the motives behind it.

The state government insists the plan will help prevent flooding of the Hawkesbury-Nepean Valley but Dr Brown argues the best protection would be to stop developments on floodplains.

“I’d like to know who’s really behind the scenes pushing for the raising of the dam which will cause extensive damage in the world heritage area,” he said.

“They’re devouring very important natural and cultural sites for really inexplicable reasons.”

Infrastructure NSW, which is in charge of the project, has previously said it will be designed and constructed to be resilient to the future impacts of climate change such as bigger floods.

But Dr Brown argues if the government is concerned about climate change causing bigger floods – they should address climate change first.

“The government is planning for disasters of their own making,” he said.

“Are they going to sacrifice the Blue Mountains heritage for the potential damage being done by opening more coalmines?”

The federal government and Labor have been contacted for comment.