A drama-filled morning at a Senate inquiry into the Murray Darling Basin has resulted in the deputy chair quitting and a state minister rejected from giving evidence.
Nationals Senator Barry O'Sullivan walked out of the committee in Adelaide and jumped on a plane back to Queensland after a media story emerged of Senator Sarah Hanson-Young criticising the hearing.
The Greens senator, also a member of the committee, said corruption had led to water theft in the basin.
"A protection racket for the Nationals," Senator Hanson-Young said.
Senator O'Sullivan said he would recuse himself from the inquiry until the comment was publicly retracted.
He said the comments undermined the regional and rural affairs committee, which is conducting the inquiry.
"(A committee) I have proudly served and prided itself for a very long time on being collegiate and always striving to work in the best interest of rural and regional Australia," Senator O'Sullivan told AAP.
"These comments are not in the spirit of this committee and the work it does."
However, Senator Hanson-Young's comment was related to federal parliament with former Nationals leader Barnaby Joyce as the water minister.
"Other states don't want to take seriously the rorting and compliance issues throughout the Murray Darling Basin," she said.
"We can't allow the parliament to run a protection racket for the Nationals."
Committee chair Senator Glenn Sterle was shocked by his deputy walking off and later told AAP he was reeling from the decision.
"Gee whiz, I don't know what we've got to do but I'd like to see Senator O'Sullivan back on this inquiry because we have so much work to do," he said.
Earlier, South Australia's Water Minister Ian Hunter made an unscheduled appearance at the hearing but was refused permission to make a statement alongside departmental officials.
A member of his department was allowed to read a statement on his behalf alleging there was corruption, water theft and systematic undermining of the basin plan.
Senator Hanson-Young said it was an atrocious decision by the chair to reject the minister's evidence.
"Often in these committees, we want to call state ministers and they refuse to come," Senator Hanson-Young said.
"To have a state minister sitting in front of us willing to give evidence and dismissing it, I think was the wrong call."
Mr Hunter agreed and described his treatment as a "terrible political blunder".
"It shows again the eastern states don't really care about South Australia's position on water - how dare we have a view about it," Mr Hunter told ABC radio.
Senator Hanson-Young said $13 billion had been spent to secure water in the basin for the environment, but the water was instead being sucked out into storage for corporate irrigators.
