Senator Nick Xenophon has given up proposed MDB changes as part of a big political deal.

Senator Xenophon wanted the Federal Government to find an extra 450 gigalitres of water to restore the health of the Murray River, and said he would not support the LNP’s ABCC bill until it did.

The Coalition was locked in late-night dealings with Senator Xenophon this week, fighting for every bit of support it could find.

In return for Senator Xenophon dropping his demand for 450 gigalitres, Prime Minister Malcolm Turnbull has written to South Australian Premier Jay Weatherill calling for more scrutiny of the Murray-Darling plan.

“I propose that we make the progress of the Murray-Darling Basin plan a standing item at every COAG meeting so that first ministers are regularly monitoring and comparing progress of the plan,” the Prime Minister said.

“The Government will also establish a special estimates process to be held twice yearly in addition to the usual portfolio hearing, enabling Senate scrutiny of all the relevant agencies to review the progress of the plan.”

The South Australian senator described the compromise as “a reset” for the Murray-Darling Basin plan that would ensure money is spent more appropriately.

“I am satisfied with the correspondence between the Prime Minister and Premier Weatherill about the commitments made, about the processes put in place,” Senator Xenophon said.

National Irrigators Council chief executive Tom Chesson said the new measures were welcome.

“As this week has again highlighted, anything which improves senators' — and other state and federal politicians' — understanding of water issues in the Murray-Darling Basin can only be a good thing,” he said.

South Australian Labor senator Penny Wong accused Senator Xenophon of selling out.

“I think it is very disappointing for all South Australians because we wanted Nick, along with every South Australian senator and member, to stand up for South Australia,” she said.

“We needed water, we didn't need more talk.”