Federal Labor will back the Greens in its bid to stop the Government changing the Murray-Darling Basin Plan.
Late last year, the Government attempted to reduce the amount of water being returned to the environment in the northern basin following recommendations from the Murray-Darling Basin Authority.
Greens senator Sarah Hanson-Young is seeking to have that disallowed, and the Senate has until next week to decide the matter.
Labor MPs at their party meeting this morning vowed to support the Greens, and are calling for a new review into the northern basin.
The changes were made in a bid to ease pressure on farmers in northern NSW and southern Queensland, where communities suffered due to a loss of water for irrigators.
As a result, the authority proposed a reduction in water recovery targets in the north of the basin from 390 gigalitres to 320 gigalitres — a 70-gigalitre decrease.
The move was described as a "sensible balance" between social, economic and environmental interests in the region.
The authority also said reducing the water recovery target would save an estimated 200 jobs in irrigation dependent communities.
Farmers say Labor's move could jeopardise jobs
Assistant Water Minister Anne Ruston, who lives in a South Australian River Murray community, said she hoped Labor would change its mind.
"I am so surprised that even in the argy-bargy political environment that we live in that Labor would be prepared to put this once-in-a-lifetime opportunity to restore river health at risk," she said.
"I am just astounded at the absolute blatant politics if they choose to go ahead with this disallowance."
The National Farmers Federation (NFF) has condemned Labor's move, saying it would jeopardise jobs without delivering environmental improvements.
The NFF had been warning that communities in the region were "nearing breaking point" and needed relief.
The Nick Xenophon Team in the Senate also called for the Government to "put the brakes" on the basin plan, until a rigorous review was completed.
"While [we] support the Murray Darling Basin being implemented in full, confidence in that implementation has been eroded over the past 12 months," Senator Rex Patrick said.
The Australian Conservation Fund (ACF) had been campaigning for the changes to be stopped, saying they would threaten the recovery of the environment.
"Over the last six months numerous revelations have cast serious doubt about whether our elected officials are ensuring the Basin Plan is being fully delivered for the benefit of all wildlife and communities that rely on the river, not just a handful of powerful irrigator," ACF director Paul Sinclair said.