The Bureau of Meteorology and CSIRO scientists' report says Australia could experience drought twice as often and the events will be twice as severe within 20 to 30 years.

This has serious implications for how taxpayers in the future help drought-affected farmers and the report says the existing definition of exceptional circumstances, which triggers eligibility for farmers' drought aid, will need to be reviewed.

The Government has budgeted to spend $760 million this financial year on drought relief payments to farmers and businesses hit by drought.

If the scientists' forecasts are correct, budgets at this level would not be enough to cover current exceptional circumstances payments.

The NFF urges more assistance to farmers for the massive investment needed to plan ahead and introduce new techniques to offset the impact of the forecast more frequent droughts.

NFF president David Crombie says,"Producers will need to adapt to climate change and this adaptation will require significant additional resources." (See separate story).