The cost of charter flights to transport asylum seekers to Nauru and between overcrowded detention centres in Australia is now costing taxpayers an average of at least 6.1 million dollars a month.
As the budget blowout of the failed border protection policy mounts, the opposition accused the federal government of spending more money on charter flights for asylum seekers than in grants to the Royal Flying Doctor Service.
The spike in costs, revealed in figures posted in government tender notices, is being put down not just to overcrowding but the government's decision to adopt the Coalition's policy of offshore processing on Nauru.
It also includes the costs of the new policy of returning economic refuge seekers to Sri Lanka.
Immigration Minister Chris Bowen's spokeswoman said the costs now included not just domestic but international transfers, including to Nauru and Manus Island, and returns to Sri Lanka.