The Murray-Darling Basin Authority has been accused of "suppressing" research findings it didn't like in formulating its target for returning a minimum amount of water to the environment.

Matthew Colloff, a senior CSIRO research scientist, will on Wednesday tell the South Australia's Murray-Darling Basin Royal Commission the authority "attempted to influence CSIRO findings on several occasions", according to his submission.

Serious claims have been made about the integrity of the science underpinning the Murray-Darling Basin Plan. Credit:Jessica Shapiro

"I was unhappy with the extent of [the authority's] interference throughout the course of the project," Dr Colloff said. "[I] felt our scientific integrity was being compromised and independence undermined."

The research centred on what would be the minimum amount of environmental water savings the $13 billion basin plan could secure in order to win the support of states and irrigators who were keen to maintain extraction rates as high as possible.