A NSW Coalition MP has called for a united front among irrigators

Describing Labor as the enemy, Ms Ley took to Twitter to say the 450GL was a line in the sand that should not be crossed.

"And if a Labor/Independent/Greens government ever tried to push it through I would do everything to get NSW to exit the Basin Plan," Ms Ley said.

The Labor Party has said it will scrap the deal to deliver the 450GL upwater to SA and remove the 1500GL cap on water buybacks in the Plan if it gains power.

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In December, the federal and basin state governments signed an agreement to send 450GL of environmental 'upwater' to SA, with water recovered through efficiency projects.

A key condition of the deal - advocated for by the Victorian and NSW governments - was that there be only neutral or positive socio-economic outcomes of recovering the water.

Ms Ley said sourcing the 450GL in the north would effectively mean buying almost all the remaining entitlement.

"It would end all northern irrigation," she said.

"You know what I really can't stand?

This 'us against them' mentality between irrigation communities, when the real enemy is Labor."

Ms Ley was responding to Deniliquin farmer Michael Hughes who said the industry would not survive if Labor pursued the 450GL.

"If the cap on buybacks is lifted and target 3200 GL's of recovery, the Murray Valley is dead," Mr Hughes said.

"Irrigation through southern NSW and northern Victoria, along with the industries and communities they support, will all go."

Ms Ley said she would again call on NSW to withdraw from the Plan if Labor was to be elected and succeeded in its proposal.

"When the northern basin disallowance motion was going through Parliament about a year ago, it looked as if Labor was going to support the Greens," Ms Ley said.

"The effect of that was the Sustainable Diversion Limits would have also fallen over, and we would have been targeted to recover the 605GL," she said.

Ms Ley said that was a very real proposition.

"At the last minute they changed their minds, but for several weeks there that was going to happen," she said.

"That would have meant coming back into communities I represent, to buy water, and that's my line in the sand, as is the buyback of the 450GL."

She said, at the time, she contacted former NSW Water Minister Niall Blair over the proposal.

"He said withdrawing from the plan was under consideration and that the states and Commonwealth could go back to water sharing plans," Ms Ley said.

"It was a real possibility, and it can be a real possibility again if some of this nonsensical agenda sees the light of day."

She said the December Ministerial Council meeting mitigated against direct buybacks.

"What Federal Labor is proposing is quite a different proposition from what all the Basin states enacted," Ms Ley said.

She said she hoped NSW Water Minister Melinda Pavey would be "feisty and determined" in protecting irrigation communities.

Victorian Water Minister Lisa Neville was also a staunch opponent of further buybacks.

"If the worst comes to the worst and the Coalition loses the election - which I don't believe it will - they would be gatekeepers," Ms Ley said.

"And I would be calling on them to shut the gate, hard."

Ricegrowers' Association of Australia President Jeremy Morton said if Federal Parliament didn't make the necessary and recommended changes to the Murray-Darling Basin Plan, it left no option for NSW but to go it alone.

He said NSW had compromised for far too long and should not be backed into a corner.