The State Government is bracing for another mass fish kill in the Darling River this week, with soaring temperatures forecast in western NSW.

Key points: Contractors will begin cleaning a 40-kilometre stretch of the Darling River this week

Contractors will begin cleaning a 40-kilometre stretch of the Darling River this week Up to a million fish were wiped out by an algal bloom earlier this month

Up to a million fish were wiped out by an algal bloom earlier this month The Federal Government wants to use $5 million of Murray-Darling Basin funds to replenish fish stocks

The mercury is expected to reach up to 46 degrees Celsius in the town of Menindee, where up to 1 million native species were killed in an algal bloom over the New Year.

The Bureau of Meteorology said a heatwave, caused by hot air being blown from Central Australia, would persist until Saturday and could break temperature records around Broken Hill.

Primary Industries Minister Niall Blair said state and local governments would work with the community to manage the possibility of another ecological disaster.

"Well we know that we've got high temperatures right across the state and a lot of poor water quality situations particularly brought on by the extended drought so unfortunately we are expecting that we may see more fish killed," Mr Blair said.

The warning comes as contractors prepare to clear the 40-kilometre stretch of the Darling River of dead fish before their rotting carcasses compound the situation.

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Federal Agriculture Minister David Littleproud will convene a meeting of State and Federal environmental and water stakeholders working under the Murray-Darling Basin Plan.

Mr Littleproud proposed using $5 million for a native fish recovery strategy and will seek agreement for the money to come from Murray-Darling Basin funds.

"The reality is we're in a serious drought and the only silver bullet is rain," he said.

Mr Blair said he would consider the $5 million payment depending on what it funded, but the critical issue was water, not cash.

"We need water to be able to address this issue, we can't buy our way out of it," Mr Blair said.

"We do have our re-stocking programs, we'll be assisting with the clean-up, but we just need water … to go down the system to try and address some of these water quality issues."

Prime Minister Scott Morrison refuted a report released by NSW Labor at the weekend claiming the Liberal Government ignored warnings about low water levels.

"I'm concerned today that some might want to play politics," he said.

"There were reports done by scientists under Labor's contribution to that plan back in 2012, the plan has been operating in accordance with that advice and so we need to just keep on working on the issue."

Mr Morrison said the fish kill was because of the drought.

"It's a devastating ecological event, particularly for those all throughout that region the sheer visual image of this is terribly upsetting," he said.

However, that is disputed by many people in Menindee, who argue poor water management has compounded the mass kill.

Opposition Leader Bill Shorten has written to Mr Morrison calling for an emergency scientific taskforce to be set up and investigate how the fish kills took place and what caused the magnitude.

Mr Shorten said the taskforce should be independent.

"This is an ecological disaster and an unfolding emergency and should be treated as such," he wrote.