Addressing the rally of about 100 people outside Parliament House in Sydney, Greens MP Ian Cohen said the tip posed “unacceptable environmental risks and mustn’t be allowed to proceed”.

“To locate a tip that has the potential to take lead paints and other hazards near waterways and national parks is pure madness,” he said.

The protest rally organised by community lobby group Shoalhaven’s Unwanted Tip (ShUT) attracted a good roll-up of participants who waved placards and chanted “treasure not trash” to highlight the tip proposal’s environmental dangers.

“Materials such as lead, a highly toxic substance to humans, could quickly contaminate waterways after heavy rains and flooding,” Mr Cohen told the rally.

“Within a couple of hundred metres of the proposed tip are the upper reaches of two river systems, both of which, of course, flood.”

Mr Cohen also spoke of massive increases in truck movements along the troubled Princes Highway and through the Tomerong township that would result from the tip.

Similar concerns were raised by South Coast MP Shelley Hancock, who also addressed the rally, urging protesters to fight back against state government regulations that took the tip decision out of the hands of the local community.

Mrs Hancock also arranged for the protesters to meet NSW Opposition Leader Barry O’Farrell, who offered a promise to overturn laws and give decision-making back to local councils.

However he could not promise to overturn any approval given to the tip by the Joint Regional Planning Panel, saying such a move may result in compensation being payable.

Others addressing the rally in Sydney included former South Coast MP John Hatton and Greens representative on Shoalhaven City Council, Amanda Findley, while Shoalhaven deputy mayor Gareth Ward spoke to the group in Wollongong ahead of the meeting with Mr O’Farrell.

All pointed out the serious social and environmental impacts of the proposal, which had led to more than 750 objections being lodged – a record with Shoalhaven Council.

“Objections to the proposal are environmental, social and economic,” said ShUT spokesperson John Levett.

“It will involve toxic leachate storage in the headwaters of both the Jervis Bay and St Georges Basin catchments, which are currently free of any polluting industry.”

Mr Levettt was confident the rally delivered a “loud and clear” message to decision makers about the danger posed to what he described as “a state asset”.