The management plan which was meant to save the Murray-Darling basin has been labelled a failure by a leading environmental professor, as the blame game over a mass fish death event in western NSW intensifies.

Up to a million fish died in the Darling River this week, with many carcasses sinking to the bottom of the river while others rot along the riverbanks.

The town of Menindee “stinks” and there are fears more fish will die as the water quality continues to worsen, local Kate McBride told AAP on Friday.

“More oxygen will be taken out of the water and the remaining fish, which are pretty much only carp, are going to continue to die – further fish kills will be seen undoubtedly,” she said.

Residents are pointing the finger at state and federal governments for draining too much water from the Menindee Lakes and over-allocating the precious resource to irrigators.

But the peak body for irrigators – the National Irrigators’ Council – has hit back, insisting farmers at the north of the river have received no water allocations in the past 12 months.

Scientists argue mismanagement of the river system is to blame although the NSW government insists the ongoing drought is a key factor.

Australian National University honorary professor John Williams says the current Murray-Darling Basin Plan has “failed” and needs to be overhauled.

“The real problem is managing the Darling under this plan has been far from satisfactory,” Prof Williams told AAP on Friday.

“The drought is simply the straw that broke the camel’s back.”

The scientist claims the plan allows too much extraction from the northern part of the system and doesn’t factor in how to manage drought.

Prof Williams admits it’s difficult but warns there’ll be more fish deaths if there isn’t a 30 to 40 per cent reduction in the amount of water extracted.

“It’s taking too much water … the fish kills point to our failure with the current implementation of the basin plan,” he said.

A South Australian royal commission in 2018 investigated allegations of water theft from the Murray-Darling basin by rogue irrigators with a report due in February.

Senior counsel assisting the commission, Richard Beasley, told AAP in a statement on Friday that the mass fish deaths are “terrible” and some of the issues raised fall within the commissioner’s terms of reference.

Only the commissioner can request additional time to consider the event but Mr Beasley on Twitter said it would be the “right thing to do”.