Disturbing mass fish deaths in NSW should not fracture bipartisan support for the Murray-Darling Basin Plan, Prime Minister Scott Morrison says.
The Greens have called for a royal commission into the management of the river system after the deaths, pointing the finger at "corrupt" irrigators.
Labor is undecided on whether it would support such an inquiry, saying it wants to see the findings of another royal commission first.
Deputy Prime Minister Michael McCormack, meanwhile, has suggested the Murray-Darling Basin Plan needs to be "tweaked".
Mr Morrison has tried to hose down the debate on the issue, saying the basin plan must maintain bipartisan support.
"I don't want to see the disturbing scene that we've seen in relation to the fish deaths trigger some sort of pre-election political game being played with what is a very important area of environmental management for the basin," he told reporters in Fiji on Thursday.
"It is too important for Australia and all of those that depend on that system, and for the future of our environment in that system."
Up to a million fish are believed to be dead in the Darling River at Menindee as the result of a cold front killing off an algal bloom which sucked oxygen from the water.
Greens senator Sarah Hanson-Young said her party would introduce legislation to the upper house for a royal commission when parliament resumed next month.
"The mass fish kill that has struck the Lower Darling in recent weeks is just the latest in a long list of problems with the management of the Murray-Darling Basin," Senator Hanson-Young said on Thursday.
Opposition Leader Bill Shorten said he wants to see the findings of a South Australian royal commission into the Murray-Darling Basin, and advice from top experts, before side deciding on the next best steps.
Royal commissioner Bret Walker is due to hand his final report to the state government by February 1.
Mr McCormack said he was committed to the bipartisan water management plan, but the rare event meant there was cause to revisit and improve it.
"It took us 100 years to reach this stage. Of course there needs to be some tweaks," Mr McCormack told ABC radio on Thursday.
"We've got the experts coming together later this month. We'll listen to the recommendations."
He said the fish deaths at Menindee were the result of unprecedented drought conditions, with the river system needing water to flush through it to stop more fish kills.
Australian Associated Press