Victoria ignored advice to order desalinated water in 2012 and regional communities are still paying the price, Water Minister Lisa Neville says.
She's ordered $637 million worth of water - 50 gigalitres - from the Wonthaggi desalination plant, which has sat idle since it was completed.
Ms Neville said the previous water minister, Peter Walsh, had rejected advice in March 2012 to order water from the plant.
"He provided his own little advice, which said that as water minister he thought it was going to rain," Ms Neville told reporters.
It did rain in Melbourne.
But Ms Neville said regional communities didn't get the benefit of extra water and they still had severe restrictions.
Opposition leader Matthew Guy said Ms Neville should leave her job if she's just going to take advice rather than make decisions.
"She's not doing her job. Other people, she claims, are making her decisions for her," he said.
Nationals leader Mr Walsh said on Sunday the decision to turn the desalination plant on was a political one, designed to save Labor some face after signing a bad contract for the plant in 2009.
Victorians pay $1.8 million a day for the plant, whether water is produced or not.
The opposition has argued for water restrictions to be put in place instead of ordering the desalinated water.
But Ms Neville said restrictions would need to be severe to have the same effect.
"This would have a significant impact on businesses, it would have a significant impact on the way we live our lives," she said.