A lawyer assisting a royal commission into the Murray-Darling Basin Plan has criticised the Federal Government for shirking its responsibilities by seeking to prevent bureaucrats from giving evidence.

In his opening statement for the first public hearing for the Murray-Darling Basin Royal Commission, senior counsel assisting Richard Beasley raised concerns about a statement from a spokesperson for Water Resources Minister David Littleproud that said compelling federal bureaucrats to testify in state-run royal commissions could "effectively stop the Commonwealth from governing".

Mr Beasley said the argument was "factually incorrect".

"It is part of the Government's job, not a hindrance to it, for it to provide an explanation of decisions it has made," Mr Beasley said.

"It's a fundamental part of the Government's job to respond to that."

In response, Mr Littleproud told the ABC the Government was "happy to answer questions about policy in appropriate forums like Question Time and Senate Estimates".

Mr Beasley's argument followed a move from the Federal Government last week to seek injunctions and declarations from the High Court that the state-run royal commission did not have the power to compel federal bureaucrats to give evidence.

The South Australian Government has said it will fight the injunction, and called on other basin states to do likewise.

Royal Commissioner Bret Walker SC said he would not be actively involved in the move by the Federal Government and Murray-Darling Basin Authority (MDBA) to limit the purview of the state-run royal commission.

"If statements in what I regard as uninformed public comment about the powers of this commission being limited territorially were to be true, I cannot resist observing that what would be true of a Royal Commission would also be true of a court," Mr Walker said.

"It would be a shocking revelation to those of us who litigate for a living in Australia, that the process of state courts have no compulsory effect outside the territories of the states."

Basin plan may be unlawful

Mr Beasley said he had been provided with evidence that the amount of water that could be safety taken from the river (ESTL) had been arrived at through an incorrect interpretation of the Water Act 2007.

"If the sustainable diversion limit for the basin plan does not reflect an ESTL there is a real risk that that part of the Basin Plan is unlawful," Mr Beasley said.

He said that there had been "no response of substance" by the MDBA to concerns raised by experts on the efficiency measures being implemented under the Basin Plan.

Commission follows allegations of illegal take

The royal commission was established by the former South Australian Government on 23 January following allegations revealed by the ABC's Four Corners that water was being illegally taken from the basin system.

Under the terms of reference, the commission has been tasked with examining these allegations, as well as whether the Basin Plan was benefiting the environment.

Mr Beasley said the commission had received 144 submissions from experts and stakeholders across Australia.

As part of its consultations, the commission also visited sites across the four basin states.

These visits included Goolwa and Murray Bridge in South Australia, Deniliquin and Bourke in New South Wales, Mildura and Shepparton in Victoria, and St George in Queensland.

Mr Beasley said the regional consultations raised a broad range of issues, including the amount of water being returned to the river system and its impact on the livelihood of regional communities and irrigators.