The NSW government is lobbying the Commonwealth to help fund its controversial plan to raise the Warragamba Wall by 14 metres.
The government has written to Canberra seeking to split the cost of the massive infrastructure project that's estimated to cost about $1.6 billion.
Premier Dominic Perrottet announced the decision to pursue the project on Wednesday, declaring it Critical State Significant Infrastructure to smooth its path through development and approval processes.
He stressed he didn't want the project bogged down in red tape and government bureaucracy, saying "we need to prepare, we need to invest".
The premier believes it is the most effective long-term flood mitigation strategy to protect communities in the Hawkesbury-Nepean, which have been repeatedly hit by floods.
Treasurer Matt Kean was spruiking the project on Thursday but acknowledged the required funding was not yet secured.
"This is the right project to protect people to protect property and ensure that we save lives so we need to crack on with it," he told reporters.
"We're calling on the Commonwealth to come to the party to help us fund this project so we can get on with the job of raising the dam wall and protecting people living on the (Hawkesbury-Nepean) flood plain," he said.
Labor and independent MPs say the decision strips the community of its voice over the project, and risk the Blue Mountains National Park World Heritage status.
Labor's Penny Sharpe said Mr Kean had abandoned the promise he made when environment minister to stand up for national parks and world heritage protection.
"Mr Kean has today endorsed the premier's breathtakingly ignorant comment to 'put people before plants'," she said.
"Together the premier and treasurer have committed the government to erasing unique Aboriginal cultural heritage and ignoring traditional owners.
"They endanger the World Heritage listing of the Blue Mountains National Park and the millions of tourism dollars and jobs that go with that and they shred any notion that this government is committed to saving threatened species."
