Some people in flood-devastated Ipswich, west of Brisbane, have reported being heavily overcharged for basic food essentials.

Fair Trading Minister Peter Lawlor says shoppers in Ipswich and Rockhampton, in central Queensland, have reported that some traders are charging $10 for bread or milk.

"The department discusses the issues with them, and if they want to lodge an official complaint - which six people have done - then they're fully investigated," he said.

"But I think traders who attempt to profit from the misery of others during the floods should keep in mind that people have long memories.

"Even if there's no official complaint, any quick returns they seek to make will be of little value to the business in the longer term."

Mr Lawlor says if there is evidence they are breaking the law, they will be prosecuted.

"Under Australian consumer law, which commenced on January 1, there are penalties of up to $220,000 for individuals who are convicted of unconscionable conduct," he said.

"But they can also issue infringement notices - penalties of about $1,300 for individuals and $66,000 for listed companies."

Ipswich Mayor Paul Pisasale says the city will remember businesses that try to take advantage of the disaster.

"I know I'm not supposed to say [this] - but the health inspectors are on their way and the building inspectors are on their way after we finish this to see if we can help those businesses - [but] like hell," he said.