An Australian citizen is among 30 people unlawfully held in immigration detention in the last financial year, according to a Commonwealth Ombudsman report.
The person, named as Mx B, was wrongfully detained by Home Affairs for 945 days — two and a half years — due to incorrect reading of Australia's citizenship laws.
Mx B was born in Australia in 1989 to New Zealand parents, briefly left, then returned in 1992, and should have been granted automatic citizenship on their 10th birthday in accordance with the Citizenship Act. But this did not occur due to "poor record keeping".
The Ombudsman report sets out a litany of departmental errors, incorrect assumptions and failed checks spanning four decades.
Three incorrect citizenship assessments
After growing up in Australia, Mx B was convicted of criminal offences and sentenced to prison in 2010 at the age of 21.
In 2018, while in jail, Home Affairs carried out a citizenship status assessment and incorrectly found Mx B was not an Australian citizen, due to their brief departure from the country as a baby.
"They [Mx B] were assessed as not having been ordinarily resident [in Australia] for the first 10 years of their life," the Ombudsman report said.
"Officers failed to consider relevant case law about absences from Australia."
In 2019, the department, acting on the mistaken understanding that Mx B was a New Zealand citizen in Australia on a special category visa, considered whether to cancel Mx B's visa on character grounds, but found their visa had ended in the 1990s.
A second citizenship assessment again determined Mx B was not a citizen, which the Ombudsman described as another "failure to consider all available information and relevant case law".
Upon Mx B's release from jail in 2022, the department placed them into immigration detention.
"Mx B claimed to be an Australian citizen on multiple occasions throughout their detention," the Ombudsman report stated.
In 2024, Mx B's legal representative sent the department correspondence regarding Mx B's claimed Australian citizenship.
"The Department completed a further citizenship status assessment for Mx B based on existing information in its systems," the report states.
For the third time, the department determined Mx B was not an Australian citizen, "failing to take into account the new information indicated by Mx B's legal representative".
Eventual release after High Court NZYQ ruling
In November 2023, the High Court's NZYQ ruling found the indefinite detention of non-citizens where there was no reasonable prospect of removal was illegal.
That triggered the release of more than 300 people from immigration detention.
Mx B was not one of them, remaining in detention until April 2025, when the New Zealand government told the Home Affairs department that Mx B was not a New Zealand citizen.
"The Department subsequently found Mx B to be affected by the outcome in NZYQ because their removal from Australia was not reasonably practicable in the foreseeable future," the Ombudsman report said.
"On the same day, the Department granted Mx B a Removal Pending bridging visa on strict conditions and released them from held detention."
A fourth and final citizenship assessment found that Mx B was an Australian citizen.
'Mx A' wrongfully detained for 304 days
Mx B is not alone. The Ombudsman report found 30 out of the 4,247 people placed into immigration detention between July 2024 and June 2025 were unlawfully detained.
Of those, 60 per cent of cases were due to a delay in communicating a ministerial visa approval to the department, leaving 18 people in unlawful detention for one day.
One individual, known as Mx A, was wrongfully detained for 304 days due to a decision maker's "incorrect understanding of the law".
Of those affected, none have filed compensation claims against the government.
The report has made three recommendations, including that the department work with the Home Affairs minister to "formalise policies and procedures relating to the communication of Ministerial intervention decision".
It also recommended Home Affairs apologise to those impacted.
The Home Affairs department has been contacted for comment.