Darwin will soon replace Christmas Island as Australia's central place for housing asylum seekers.
Plans have been announced to add 19 hundred new beds to the Northern Territory capital.
Immigration Minister Chris Bowen says this includes a plan for a new 15 hundred bed facility at Wickham Point on Darwin harbour.
The first 500 beds at Wickham Point are expected by mid-year, he said.
This will take Darwin's immigration detention capacity to almost three-thousand eclipsing Christmas Island's ability to hold 26 hundred.
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Opposition immigration spokesman Scott Morrison says the government is embarking on a detention bed binge.
An existing centre at Darwin airport will also be expanded.
The Scherger RAAF Base near Weipa in Queensland would continue to be used as detention accommodation for another 12 months, Mr Bowen said.
He said the expanded mainland facilities would relieve pressure on the Christmas Island centre.
Mr Bowen said work on the Wickham facility would begin in coming weeks, subject to final planning approval.
Case managers, mental health expert, medicos and interpreters would be available at this site.
The minister said the privately leased facility was more cost-effective, and had the support of the Northern Territory government.
Another 400 beds would be added to the Darwin airport site by mid-year.
By this time, asylum seekers would no longer be housed at Virginia Palms in Brisbane.
The Asti Hotel in Darwin would also cease to hold those seeking refugee status.
The government has also discontinued a previously announced contingency option of expanding the Melbourne Immigration Transit Accommodation to house more families and minors.
"The government's decision to move children and vulnerable families into the community makes expanded use of the facility unnecessary at this stage," Mr Bowen said.
He said the Weipa community supported the decision to have the Scherger RAAF Base house asylum seekers for another 12 months, until June 30 2012.
The base will not be needed for military uses during that time.
