The operators of popular Brisbane burger restaurant chain Miel Container may be in hot water after allegedly underpaying staff more than $155,000.

The Fair Work Ombudsman has kicked off legal action against brothers Johnny and Sanghoon Na, who own and operate the businesses in Brisbane’s CBD and Sunnybank, claiming 11 overseas workers were paid flat rates as low as $10 an hour.

Acting Fair Work Ombudsman Kristen Hannah said a decision was made to commence legal action because of the blatant nature of the alleged underpayments and the involvement of vulnerable overseas workers.

“We treat exploitation of overseas workers particularly seriously because we know they can be vulnerable if they are not fully aware of their rights, face language barriers or are reluctant to complain,” Hannah said in a statement.

“We are committed to actively pursuing and holding to account any employer in Australia who thinks they can get away exploiting overseas workers.”

Miel Container allegedly underpaid eight employees at the CBD store $111,652.09 over a three-year period between 2013 and 2016, and five employees at the Sunnybank outlet $44,162.20 over a seven-month period in 2016 (two staff worked at both outlets, hence the 11 cases in total).

The South Korean nationals were in Australia on working-holiday and student visas and were employed on a casual basis in the kitchen and front-of-house. According to the Fair Work Ombudsman, most spoke limited English and one junior employee at the Brisbane CBD outlet was only 19.

Inspectors allegedly discovered that employees had not been paid any wages for up to seven days of work during “trial periods” and were then generally paid flat rates ranging from $10 to $16 an hour.

Under the Restaurant Industry Award 2010 at the time, they were allegedly entitled to have been paid up to $20.61 per hour for ordinary hours and higher rates for weekend, public holiday and overtime work.

Johnny Na, the sole director of Miel Container Pty Ltd and HWMJ Pty Ltd, the companies under which the businesses operate, told Broadsheet he had no comment to make in response to the allegations other than that they “were wrong”.

Na will face court for allegedly being involved in some underpayments as well as record-keeping and payslip contraventions at the two outlets. His brother Sanghoon Na, a co-owner and manager of the Sunnybank store, will face court for allegedly being involved in some record-keeping contraventions at the southside outlet.

While the workers have been partially back-paid to date, the Fair Work Ombudsman is seeking court orders for full back-payment to the employees. A directions hearing is set to take place in the Federal Circuit Court on November 20.