"South Australia's biggest export is extortion," he said.

Similarly, Senator Leyonhjelm said not a drop of the disputed 450 billion litres should be sent down the Murray because it would hurt irrigators upstream..

"Nick can go and get f---ed, South Australia has no right to claim any more water," he said.

Under the agreement, the federal government would pay hundreds of millions of dollars to improve irrigation infrastructure with the aim of freeing up 2750 gigalitres to be sent down the Murray River as environmental flows by 2024.

Another 450GL would be also sent down but only, as the agreement stipulated, if there was no adverse social or economic effects on upstream communities.

The issue exploded a week ago when Mr Joyce, NSW and Victoria said there would be adverse effects and the extra 450GL should not be sent down the river. South Australia argues this breaches the spirit of the agreement.

Trade unions, vehemently opposed to the ABCC, have seized the opportunity and have been robo-calling voters in the NXT-held Adelaide seat of Mayo, urging they demand NXT stand up for what is a potent political issue in South Australia: water.

Senator Xenophon, who held talks in Canberra on Sunday with Mr Turnbull and Workplace Relations Minister Michaelia Cash, said he was unfazed by the union campaign and was trying to find a way through on the issue.


He defended horse-trading water over the ABCC, saying, if the Murray-Darling Basin agreement could be broken, "that would obviously shake our confidence in the government".

Mr Turnbull has put it on the agenda for next week's COAG meeting with the premiers and territory leaders but this will be after Parliament rises for the year.

Senator Xenophon said Mr Turnbull would need to do more. He believed billions of litres of extra water could be freed up, for example, by reducing evaporation at the Medindee Lakes, which meant there could be enough for irrigators as well as some extra to send down to South Australia for environmental flows.

He would not give the government the green light on the ABCC or any other legislation until the South Australian Labor government was satisfied. The Senate is scheduled to start finalising debate on the ABCC bill on Monday.