The Queensland floods that inundated most of the state and crippled many of its major industries could possibly be the most expensive disaster in the country says Federal Treasurer Wayne Swan.

The floods affected more than 28,000 properties and displaced the 2.1 million people living in the state.

"It looks like this is possibly going to be, in economic terms, the largest natural disaster in our history," Swan said. "It will involve billions of dollars of commonwealth money, and also state government money, and there's going to be impacts on local government as well.

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"This is very big ... It's not just something which is going to occupy our time for the next few months. It will be a question of years as we go through the rebuilding process ..." he added.

Swan said the government is aiming to return the budget to surplus by 2013 but there would be some tough decisions ahead to achieve that. "We're on track to come back to surplus in 2013," he said. "We've got in place a very strict set of spending guidelines.

"There's no doubt that the costs involved in responding to this natural disaster are substantial, but we shouldn't forget that we've also got a very strong economy, a strong investment pipeline, and strong public finances."

Currently, the death toll from the floods stands at 18, with 14 others still declared missing.