The man investigating the politically charged Murray-Darling Basin Plan (MDBP) has indicated his royal commission will find parts of the plan are in breach of the Water Act.

Key points: Tony Burke was the water minister when the politically charged plan was developed

Tony Burke was the water minister when the politically charged plan was developed He did not make contact with the royal commission until January 19 as he thought it would be "inappropriate"

He did not make contact with the royal commission until January 19 as he thought it would be "inappropriate" Commissioner Bret Walker SC said Mr Burke's recollections were not consistent with contemporaneous records

Commissioner Bret Walker SC, who is due to deliver his report to the South Australian Governor on Tuesday, has dismissed recollections from former federal water minister Tony Burke that the sustainable level of water "take" was determined purely on environmental concerns.

Last week Mr Burke, who was water minister when the plan was developed, wrote to Mr Walker to express concern about the potential findings of the inquiry.

He cited suggestions the development of the plan to safeguard the river system took into account a 'triple bottom line' approach of environmental, social and economic factors.

"This does not accord with my recollection," Mr Burke said.

"My recollection of the advice that I received and the approach taken, was that the sustainable level of take had to be determined based on the requirements of the health of the Basin.

"How that was then delivered could be optimised, in line with the Water Act and the international agreements that underpin it, taking into account environmental, economic and social concerns."

The next day, Mr Walker responded.

"The submission made to me by counsel was that what you fairly call 'economic and social concerns' did affect the ultimate determination of environmental parameters — although in a manner still not disclosed by the [Murray-Darling Basin Authority]," he wrote.

"I note you say that your recollection is that you were advised that the ESLT [environmentally sustainable level of take] was not determined by a 'triple bottom line' approach.

"Assuming your recollection to be correct, the advice you were given is not consistent with the contemporaneous records and reports tendered at the commission hearing."

In his closing submission to the inquiry, counsel assisting the royal commission Richard Beasley SC said taking into account social and economic factors when setting environmental flows had "misinterpreted the Water Act … in a crucial way".

Mr Walker also criticised Mr Burke's delay in contacting the commission.

The former minister said he thought it "inappropriate" to "make direct contact with the commission at any time until now", because he had been standing alongside then South Australian Premier Jay Weatherill at the press conference announcing Mr Walker as the head of the inquiry.

"I am sure you appreciate that your letter dated 22 January 2019 has arrived at the royal commission far too late for me to give the matters in it substantive attention. Nor can it form part of the evidence of the commission," Mr Walker responded.

"Multiple opportunities were made available during the course of the commission for persons to engage with our work.

"As you are a former federal water minister, and the relevant minister at the time of the enactment of the Basin Plan, I would have welcomed any contribution you sought to make."

The MDBP has been mired in controversy and conflict since it was signed in 2012, due to the difficulties in balancing environmental pressures and demands for access to water from industries such as irrigators.

Staff from the organisation that implements the plan, the Murray-Darling Basin Authority (MDBA), were blocked by the Federal Government from giving evidence to the inquiry.