South Australia's Water Minister Ian Hunter says he wants an independent review of the New South Wales Government's handling of River Murray water, after serious doubts were raised about the effectiveness of the multi-billion-dollar Murray-Darling Basin Plan.

Key points: Last night's Four Corners broadcast a tape of NSW bureaucrat Gavin Hanlon offering documents to irrigators

Last night's Four Corners broadcast a tape of NSW bureaucrat Gavin Hanlon offering documents to irrigators Downstream, South Australia wants an inquiry into NSW's role

Downstream, South Australia wants an inquiry into NSW's role The Nationals have warned against 'demonising' irrigators

The ABC's Four Corners program last night revealed that the top water bureaucrat in NSW, Gavin Hanlon, secretly offered to share government information with irrigation lobbyists via a special Dropbox account to help them to lobby against the water management plan.

Four Corners' recording of the 2016 teleconference also revealed the NSW Government has been actively considering plans, in discussion with irrigators, to abandon the Basin Plan altogether, and has sought legal advice about doing so.

It also revealed allegations that some irrigators in the Barwon-Darling had tampered with their pump meters, masking the amount of water they had drawn from the river.

A former water compliance investigator told Four Corners that when he raised those concerns within the NSW bureaucracy, his plans for further investigation were thwarted.

Mr Hunter called for an urgent COAG meeting to commission a judicial inquiry, saying it was needed to determine how much was known by members of the New South Wales Government.

"The New South Wales Government must answer the allegations made on tonight's Four Corners program," he said.

"If the allegations are correct, that at a very senior level in the public service in New South Wales that people have turned a blind eye to this, then that is very concerning."

"There needs to be an independent judicial review — independent of government [and] independent of politics — [with] a senior judicial figure, because this strikes at the very heart of the public service in New South Wales, if the allegations are correct.

"For the sake of the delivery of the Murray-Darling Basin Plan, there needs to be a degree of community confidence.

"If you don't have confidence in the amount of water that's being taken out… then you can't actually have any compliance under the plan whatsoever.

"It's very disappointing to see what we thought was a jurisdiction acting in good faith, that at some level … they haven't been acting in good faith."

Labor, Greens want inquiry

Federal shadow water minister Tony Burke accused the NSW Government of intentionally trying to undermine the Murray-Darling Basin Plan.

Mr Burke, who was the water minister when the plan was signed, said Labor would back an inquiry.

"The whole concept of the plan is based on reserving some water for the environment to make sure the rivers are healthy," he said.

"There's no doubt there are some people within the NSW Government who are trying to undermine the plan, there's no doubt there are some people within the NSW Government who have no respect for the health of the river."

South Australian Greens federal senator Sarah Hanson-Young said she would call for a Senate inquiry into the entire Murray-Darling Basin Plan when Parliament returned in August.

"We've heard such serious allegations that things are not working properly, that the taxpayer is being ripped off [and] that the environment is being ripped off," she said.

"It's the Parliament's job to investigate what's going on and work out how to fix it."

South Australian NXT senator Nick Xenophon called the allegations "scandalous" and called on NSW's own anti-corruption watchdog, ICAC, to investigate.

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Broken Hill Mayor Darriea Turley joined calls for an inquiry, saying she was "absolutely outraged" by the report.

Concerning and corrosive: Murray-Darling Basin Authority responds

While some have called for the Murray-Darling Basin Authority to step in to address allegations on non-compliance in NSW, the agency's CEO said that was not its role.

Phillip Glyde said that, under the constitution, states retain responsibility for water management and regulation, and the Basin Plan does not change that.

He said the allegations raised by Four Corners must be thoroughly investigated, and said they are "quite corrosive" of the fragile trust that exists between river communities and governments.

"When the water level is low, people get very concerned about whether everyone is doing the right thing," he said.

"You have to have trust in that system in order to go through that reform.

"The Basin Plan is a long and painful reform and unless all of the players — whether they're from an environmental perspective, a conservation perspective, a water-use perspective — they all have to have faith that the rules are being implemented fairly right across the Basin.

"Issues like this do certainly undermine confidence, and undermine trust."

National Party MP Mark Coulton, whose electorate of Parkes spans one-third of the Murray-Darling Basin, said water buy-backs had devastated local communities.

But Mr Coulton has also cautioned against "demonising" an entire industry.

The Murray-Darling Basin Plan is a bipartisan agreement signed in 2012 that governs how to use the water that flows down the nation's longest river system.

Four states — NSW, South Australia, Victoria and Queensland — are part of the agreement.

Ecologist says many knew some were 'rorting the system'

Sorry, this video has expired Drone footage of the Barlow water reserve

Ecologist and Coorong researcher Professor David Paton said the allegations of illegal extraction from the River Murray were not "surprising", but still saddened him.

"I think many of us had appreciated that there were certain entities within the system that were rorting the system — I think it was pretty clear that it was going on," he said.

"The sad thing is, the environment is still suffering. The key for the long term sustainability of the river is actually fixing the environment.

"The thing which makes me angry is the inability of the government agencies and their senior bureaucrats, from the politicians down — and it would probably go as high as the Prime Minister — to say this has to stop."

However, Ian Cole, a spokesman for water users on the Barwon Darling system, denied the New South Wales extraction rules were out of step with the Murray-Darling Basin Plan

"To say that environmental water is being pumped is just a nonsense because in every way there are limits on the pump size you can us, there are limits on the number of pumps you can have, there are daily limits for you to pump on," he said.

Mr Cole said on a long-term average, 94 per cent of the flow in the Barwon Darling was environmental, with only 6 per cent set aside for other uses including irrigation.