Federal Opposition Leader Kevin Rudd has refused to support water sharing between the parched south-east Queensland corner and the NSW north coast's largest river system.
Mr Rudd on Friday said there was "no logical basis" for a diversion program from the Clarence River to Queensland's south-east.
This was due to the Queensland government's much-touted water grid for the region, Mr Rudd said.
The grid is designed to generate enough water from numerous sources to avert a looming water shortage as the relentless drought continues to bite.
"Therefore, it is difficult for me to see any basis, logical basis, for a diversion program from these Northern Rivers," Mr Rudd told reporters on Friday in Grafton.
Federal Water Resources Minister Malcolm Turnbull said Mr Rudd's comments demonstrated he "cannot be trusted with south-east Queensland's water future".
"So much for his commitment to Queensland," Mr Turnbull said.
"So much for having an open mind or a vision for a sustainable water future in Australia."