Senator Hanson-Young, a South Australian, told the Senate five years after the plan had been adopted, there had been investigations in allegations of water theft and corruption and there was no way of telling how much water was actually being delivered to the river system.

The opposition announced last week it would back Senator Hanson-Young's second disallowance motion regarding the 70GL. With Labor support and that of the Nick Xenophon Team's two senators, plus South Australian conservative Cory Bernardi and Victorian independent Derryn Hinch, the Greens had the numbers to have the disallowance motion passed.

But Mr Littleproud went to work on Mr Burke to try to get him to backflip after a revolt by NSW and Victoria.

The Australian Financial Review understands federal Labor had been demanding compliance measures be beefed up to police irrigators' water use after complaints about a lack of metering in return for not supporting the disallowance motion on the 70GL.

Water Minister David Littleproud: a separate proposal to make an additional 605GL available to irrigators in the southern basin remains in the balance. Andrew Taylor

It is also believed the opposition wants certainty from the government the 450GL will be delivered to the environment in return for voting against that disallowance motion in May.

Labor Senate leader Penny Wong said the opposition wanted guarantees water paid for by taxpayers went to where it was needed.

For the NSW government, the loss of the 70GL for irrigators is a red line, with the state's Water Minister, Niall Blair, warning on Tuesday disallowance was a vote to kill the plan.

The parliamentary fight over the disallowance motions has also prompted Victoria to threaten to the pull out of the basin plan, however there are hopes the Andrews Labor government could stay in the plan if it can be reassured irrigators will get their 605GL increase.

South Australia has objected to the authority's proposals to give the extra water to irrigators despite the authority's assessment they are scientifically sound, and has indicated it could launch High Court action to keep the original plan intact.