Member for Cootamundra Steph Cooke has said premier Chris Minns has lost control following Labor supporting a Royal Commission into water management.

According to Ms Cooke The NSW Government has 'spectacularly' contradicted the premier by voting in support of the motion that called for a Commonwealth Royal Commission only hours after the Premier had told the Legislative Assembly that he didn't back the proposal.

Last week in the NSW Parliament there was a Public Interest debate on a motion calling for the Royal Commission, including the implementation of the Murray-Darling Basin Plan.

Ms Cooke, as the Shadow Minister for Water, said the reversal exposed depp confusion and a lack of leadership at the heart of the state government.

"On one of the most critical issues facing regional New South Wales, the Premier said one thing in Question Time and his Government did the exact opposite on the floor of Parliament just hours later," Ms Cooke said.

"This is not a major slip-up, it is a glaring sign that the Government cannot keep its story straight on water, which is the most important resource our communities rely on."

According to Ms Cooke, unlike the Government, the coalition is united in supporting a Commonwealth Royal Commission into water management after years of flawed policy and growing concern in basin communities.

"Protecting water for the environment does not have to come at the expense of farmers, who have already contributed more than any other group to delivering the Murray-Darling Basin Plan through on-farm efficiency works and buybacks," Ms Cooke said.

"When farmers have less water, it costs more to grow food, and NSW families feel that every time they stand at the supermarket checkout.

"That is the real-world impact of poor water policy."

Ms Cooke pointed out that the premier had previously served as Shadow Minister for Water between 2016 and 2019.

"In August 2019, he and the Member for Cessnock, Clayton Barr, supported a Public Interest Debate calling for a Royal Commission into water management," Ms Cooke said.

Mr Barr was the only Government member last week to speak during the Public Interest Debatre and argued against the same idea he had previously backed years earlier.

"Despite this, he did not move to divide the House or take any step to prevent the motion from being agreed to," Ms Cooke said.

"After more than a decade of missteps and mistrust in water policy, communities across New South Wales deserve transparency and accountability.

"The outcome of this debate shows there are members of the Government who know the system is not working, even if their own Premier will not admit it.

"Without a full and independent inquiry, we risk standing in this Parliament in 10, 20 or 30 years' time having the same arguements, about the same failures, while regional communities continue to pay the price."