A former Sri Lankan military commander is an operations manager at the Manus Island detention centre which houses 30 Tamil asylum seekers.
The Human Rights Law Centre has called on the Abbott government to remove Mr Dinesh Perera from the centre.
"It is completely inappropriate to have a former military officer from Sri Lanka in charge of the welfare and wellbeing of vulnerable asylum seekers," spokeswoman Emily Howe said in a statement.
Hiring a former military commander from a refugee source country showed either failure to conduct due diligence in the hiring process or a "callous disregard" for the brutal experiences of many detainees, she said.
Mr Perera, according to his LinkedIn profile which disappeared from the internet on Monday, has been acting manager for contracted security firm G4S at the centre.
He has operational command experience as a former commander in the Sri Lankan Army.
A spokesman for G4S said Mr Perera was an operations manager but was not in charge of the centre.
"He is an Australian citizen who has worked for G4S for a number of years in other contracts before taking on a role with the Manus Island contract. He is appropriately qualified for his role," the spokesman said.
Immigration minister Scott Morrison said the appointment was a matter for G4S.
He said Manus Island was run by the government of Papua New Guinea and G4S was one of the service providers.
"Who was employed by G4S is a matter for G4S. G4S was appointed by the previous government. We're haven't continued their contract. They are finishing up there over the next six weeks," he told Sydney Macquarie radio.
Australian Tamil Congress spokeswoman Sam Pari said, if Mr Perera's background with the Sri Lankan military was confirmed, Australia was no longer simply turning a blind eye to Sri Lanka's persecution of Tamil people but was aiding and abetting it.
She said many Tamil asylum seekers claimed their main reason for seeking asylum was fear of persecution from the Sri Lankan state and military.
"We have Tamils fleeing a military accused of war crimes. They are then detained and held in the custody of a former member of that very military," she said in a statement.
"This man has access to all their personal details. Then they are returned back to Sri Lanka, after which their fate is not known."
