South Australian Water Minister David Speirs has survived a no-confidence motion in state parliament over his handling of negotiations for water flows down the Murray.
Opposition Leader Peter Malinauskas called on the minister to resign after failing to stand up to other states in protecting South Australia's interests.
Mr Malinauskas said the upstream states knew that all they had to do was hold the line on their own demands and Mr Speirs would "sell us up the river".
"The upstream states of NSW and Victoria saw him coming," Mr Malinauskas told parliament speaking to his motion on Thursday.
The opposition also pointed to criticism of the minister in the recent report of the royal commission into the Murray-Darling Basin Plan.
In his report, Commissioner Bret Walker was scathing of Mr Speirs in relation to a meeting in December, where South Australia joined with other states to agree to terms on how environmental water would be returned to the basin.
The meeting agreed to return up to 450 gigalitres of extra water to the environment, provided it did not have a negative socio-economic impact on river communities.
In return, South Australia received $70 million of federal funding to help rehabilitate the Coorong wetlands.
Mr Walker found that the agreement was against the state's interests and was almost certainly a breach of the ministerial code of conduct.
But Premier Steven Marshall told the parliament there had been no breach of the code and rejected suggestions Mr Speirs had not acted in SA's best interests.
Mr Marshall said the minister considered the situation South Australia was faced with, consulted with government officials and had the unanimous support of state cabinet.
"So, far from being a kneejerk reaction this was a carefully considered decision and, I might say, a decision we would make again," the premier said.
The opposition motion was defeated along party lines, 25 votes to 16.
