Deputy PM Wayne Swan said the recent floods would rank as one of Australia's most costly natural disasters ever.

More than 30 people have been killed since flooding began last month.

In Queensland, which has witnessed the worst of the flooding, nine people are still missing.

Floods tore through the towns of Toowomba and Grantham. But record rains have shifted the flood emergency focus from the north-eastern state to Victoria in the south-east, which is experiencing its worst floods since records began 130 years ago.

The Victoria State Emergency Service (SES) has issued evacuation warnings for communities east of the city of Kerang, which remains cut off.