People smugglers would have filled boats with children if the Gillard government had advertised a "no children in detention" policy, former immigration minister Chris Bowen says.
Although he thought children should not be held in detention for long periods, offshore processing was necessary, Mr Bowen told an inquiry into children in detention on Tuesday.
"I was not going to be in a situation where a decision I authorised led to a boatload of children drowned at sea," he said at an Australian Human Rights Commission (AHRC) inquiry.
When Mr Bowen became immigration minister in September 2010, one of his first decisions was to remove children from detention at Christmas Island.
But in 2011, he reintroduced offshore processing, opening the Manus Island centre for children and adults.
AHRC president Gillian Triggs raised concerns there was a conflict of interest between the role of an immigration minister and his guardianship of unaccompanied minors.
"This area could be reformed," Mr Bowen responded.
The minister revealed he had made inquiries into separating the roles but it was not a priority.
The immigration minister could always overrule any decision made by a guardian, he said.
Despite Mr Bowen's efforts to move minors into the community, the number of children held in detention centres skyrocketed during his time as immigration minister.
The Labor government could not keep up with the boat arrivals, he said.
"People were being released as fast as the system could bear," Mr Bowen said.
Suitable accommodation and case workers needed to be allocated to asylum seekers before they were moved into the community.
The Abbott government's indefinite detention of asylum seekers on Christmas Island was a concern, he said.
Mr Bowen was the last witness at the inquiry, which concluded on Tuesday.
The commission is preparing its draft report for the immigration department.
