Allegations of water theft and meter tampering in New South Wales have forged an unusual alliance between sworn political enemies in South Australia.

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Senators from across the political divide have joined forces to back the SA Government's call for a judicial inquiry to investigate allegations aired by the ABC's Four Corners program last week.

They include the Australian Conservatives' Cory Bernardi, the Greens' Sarah Hanson-Young, Senate Leader Penny Wong from Labor and SA Independent Nick Xenophon.

They held a joint press conference at the SA Parliament with State Premier Jay Weatherill.

"The reason we need a judicial review is to understand the truth or otherwise of those [Four Corners] allegations," Mr Weatherill said.

"If the allegations are true, they amount to the largest single jurisdiction in the Murray-Darling Basin conniving at, or actively assisting people to evade their responsibilities under the Murray -Darling Basin Plan."

Senator Bernardi said he was prepared to share a podium with the Greens and Labor on the issue to represent the interests of SA.

"If we are going to have any confidence that South Australia is getting a fair deal and a fair go, then we need to make sure that the entire agreement is being upheld, that the processes are upheld with integrity and transparency," he said.

Yesterday, Prime Minister Malcolm Turnbull announced the Murray-Darling Basin Authority would review cases of water theft, but Senator Bernardi said that was insufficient.

"The Four Corners report has scratched the surface of what could be a significant issue," he said.

"It is too big an issue for it to be investigated by those with their own interests at heart."

Senators take aim at Federal Water Minister

Senators Wong and Hanson-Young took aim at Federal Water Minister Barnaby Joyce, who last week described the Four Corners investigation as an attempt to take more water from irrigators.

"Barnaby Joyce as Water Minister is a disaster for the management of the Murray-Darling Basin and for South Australia," Senator Hanson-Young said.

Senator Wong said Mr Joyce had demonstrated he could not be trusted with the water portfolio.

"I have one message for Malcolm Turnbull: you can't hide behind Barnaby," she said.

"You can't hide when it comes to the River Murray.

"What we want is a judicial review. We want you to show some leadership."

The group called on the Prime Minister to launch a judicial inquiry. ( ABC News: Nick Harmsen )

Claims from NSW of further allegations

Senator Xenophon said his office was doing due diligence on a number of further allegations that had emerged in the wake of the Four Corners program.

"There are people calling us from New South Wales saying that significant amounts of money were spent supposedly on water saving measures, only to be undermined, only for the opposite to happen after tens of millions of dollars were spent," he said.

"What we are seeing unfolding here is potentially one of the biggest public policy scandals we've seen in many years."

Senator Xenophon said it was clear the issue transcended politics and was an issue that we must get "to the bottom of through a judicial inquiry with the powers of a royal commission".

He said it could "protect whistle-blowers and compel witnesses to give evidence, because otherwise we will never get to the truth of this".

The senators were joined at the press conference by irrigators from western NSW and South Australia's Lower Lakes.

Robert McBride from Tolarno, Peppora and Wyoming Stations south of Menindee in NSW warned the Four Corners allegations are just "the tip of the iceberg".