Casual workers employed as fruit pickers in Queensland's Gatton region have received $70,000 in back pay after an investigation by the federal Workplace Ombudsman uncovered significant underpayments against 467 employees.

Australia's Workplace Ombudsman, Nicholas Wilson, said a number of businesses in the Lockyer Valley were investigated after allegations of underpayments of hourly rate, non payment of overtime and failure to produce written piece rate agreements between the employer and workers.

Workplace inspectors from the Ombudsman's Queensland office served a notice to produce document to two businesses in November last year and an audit of time and wage records was completed that established breaches of the Fruit and Vegetable Growing Industry Award – State 2002 and the Workplace Relations Act.

"With the investigation still underway we are hopeful of recovering even more money for these workers who have been stripped off their lawful entitlements," Mr Wilson said.

Mr Wilson said many of the workers were backpackers and those likely to be vulnerable to exploitation.

"We also found employers were not maintaining wage and time worked records which was disappointing," he said.

"Without employers keeping accurate records, it is often hard to determine if employees are being paid appropriately."