She said farmers should be feeling uncertain about their future under the Coalition because they don't have a clear or united position on the best ways to tackle reform in the Basin.

When asked about the Coalition's unity on the issue last week, Nationals leader Warren Truss, said there was a clear plan for restoring the health of the Murray, but it would have a focus on the communities which lived in the basin too.

Listen to Lucy Knight's extended interview with Penny Wong

He said the promise of a referendum by leader, Tony Abbott, would be an absolute last resort.

Senator Wong said the Opposition's credibility on the Murray Darling Basin could be "measured by what they failed to do for 12 years".

"All the things they say now that they will do are all the things they didn't do over 12 years in government," Senator Wong said.

"Their position on water seems to change depending on who is speaking.

"It's interesting to compare what the Liberal Party are saying in South Australia to what Senator Joyce says in NSW and Vic.

"I don't think it's fair or reasonable for the Coalition to be telling people one thing in Adelaide and another thing in Bourke or in the Murrumbidgee.

"I think that does create uncertainty. This is a tough challenge; it's not going to be dealt with by people pretending to tell people what they want to hear, even if it isn't consistent."