The Home Affairs Department has admitted it did not seek any advice from experts in Fijian citizenship law before cancelling the citizenship of terrorist Neil Prakash.
Late last year, Home Affairs Minister Peter Dutton announced Prakash would be stripped of his Australia citizenship as a result of his criminal behaviour.
He is currently detained in Turkey awaiting trial on terror charges.
The Australian Government justified the decision by saying it was satisfied he had claim to citizenship of Fiji, through his father.
But Fijian officials have disputed that, saying they have no evidence of Prakash or his parents ever being Fijian citizens.
Shadow Attorney-General Mark Dreyfus led the questioning of department official Linda Geddes.
Dreyfus: "Did the Department or the Minister for Home Affairs obtain any legal advice, or any advice at all from experts in Fijian citizenship law before Mr Dutton made his announcement on the 29th of December 2018?"
Geddes: "No, we did not."
Dreyfus: "Did the Australian Government ever take any steps to verify Mr Prakash's citizenship status with the Fijian authorities?"
Geddes: "No. No, we did not."
Mr Dreyfus questioned Special Counsel Ian Deane, who gave the advice the Government relied on to strip Prakash's citizenship.
"The question of whether he's a citizen of Fiji is a matter of foreign law," Mr Deane said.
"I'm not at liberty to go into the details of the advice."
Dreyfus: "Did you give unequivocal advice?"
Deane: "I gave strong advice."
The revelations came as parliament's powerful intelligence and security committee examined proposed new laws expanding the government's ability to strip citizenship from all convicted terrorists, regardless of the severity of their sentence.
The Home Affairs Department has dismissed accusations the legislation is too heavy-handed and unconstitutional, arguing it is necessary to protect the community.
Prime Minister Scott Morrison met with his Fijian counterpart Frank Bainimarama earlier this month, but Mr Morrison said the matter did not come up in their discussions.
