Some CSIRO staff have decided not appear before South Australia's Royal Commission into the Murray-Darling Basin.

The inquiry has been told that some CSIRO staff will wait for the outcome of the federal government's High Court challenge over the appearance of Commonwealth employees before they turn up.

Counsel assisting Richard Beasley said it is “disappointing” that staff at Australia’s national science body are unwilling to give evidence on “purely science related” matters.

“It's disappointing because it doesn't seem to me, having looked at the act creating the CSIRO, to be particularly consistent with some of the purposes for which the CSIRO was created, including giving advice on matters of scientific debate or controversy,” he said.

Mr Beasley said it is hard to understand how the decision relates to the High Court process, as that matter relates only to the commissioner's power to compel witnesses to appear.

“The stance taken by these people or the stance they are being directed to take is not disrespectful to the High Court, it's certainly not respectful to the High Court and, in my submission, is irrelevant to the High Court,” he said.

Earlier, former CSIRO scientist Matthew Colloff had given evidence that included his concern about the extent of the Murray-Darling Basin Authority’s interference throughout the course of the project.