A Queensland restaurant operator who claimed a worker ate too much food and used too much air conditioning has been fined $21,000 after refusing to reimburse the underpaid staffer.

The owners of Fire and Stone restaurant at Tangalooma Island Resort on Moreton Island illegally paid a Chinese backpacker $10 an hour in 2014.

At the time the worker was aged in her 20s, spoke limited English and was in Australia on a working holiday visa.

She contacted the Fair Work Ombudsman which found she was underpaid $1,577 in just 19 days, having received less than half the legal rate of pay for a casual hospitality worker.

The ombudsman took the business to court after it refused to reimburse the backpacker on the grounds she "ate too much food and used too much air-conditioning".

Penalty to serve as a warning, judge says

The Federal Circuit Court found the restaurant misclassified the worker as an independent contractor and breached sham contracting laws.

It penalised owner/operator Jia Ning Wang $3,500.

Wang's company - Golden Vision Food and Beverage Services Pty Ltd – was penalised a further $17,500.

Judge Michael Jarrett found Wang had not displayed any genuine contrition or remorse, and said the penalties should send a message to the hospitality industry and employers of visa holders.

The penalties should "serve as a warning to others that similar conduct can have serious consequences and ought not be repeated," Judge Jarrett said.

Fair Work Ombudsman Natalie James said that deliberate exploitation of vulnerable workers would not be tolerated.

"We treat alleged underpayment of visa-holders particularly seriously," Ms James said.