The National Farmers' Federation is calling on tomorrow's Council of Australian Government meeting to commit to principles for assistance to irrigators in the Murray-Darling Basin and prevent any further ad hoc drought responses on a State-by-State basis.

NFF water taskforce chair Laurie Arthur says any assistance to farmers must not undermine the water market.

His call comes in the wake of the South Australian Government entering the water market to buy water on irrigators behalf to keep alive permanent plantings.

"COAG must establish assistance principles – consistent across the Basin – that do not create third-party impacts," Mr Arthur said.

"While South Australia – in a well meaning attempt to assist its irrigators – announced their intention to enter the temporary water market to buy water for its irrigators, such a move contravenes COAG's principle of 'competitive neutrality'... in effect, giving South Australian irrigators an unfair advantage."

"Rather than pursue any more ad hoc responses, tomorrow’s COAG meeting must restore genuine, consistent measures that assist the Basins irrigation communities in their time of greatest need."

Mr Arthur said an exemption from fixed water charges – which apply to water allocations regardless of their being no water – until the drought breaks would be a good move which was "both economically viable and responsible".