Asylum seekers who arrive on Christmas Island will be given the right to challenge any rejection of refugee claims in Australian courts following a High Court ruling in favour of two Tamils.
But the federal government insists the offshore detention regime will continue, warning of processing delays in light of Thursday's unanimous legal decision.
Two Sri Lankan men, known as M61 and M69, were found to have been denied procedural fairness in seeking refugee status, after arriving on Christmas Island by boat in 2009.
Under existing laws, asylum seekers who arrive in northern Australian waters are unable to appeal a decision by the Immigration Department.
This occurred because the Howard government excised these areas from the migration zone in 2001.
But the High Court ruling will enable asylum seekers to go to an Australian court if their refugee claims are rejected, giving them the same legal protections as visa overstayers who arrive on the Australian mainland.
Delays expected
Immigration Minister Chris Bowen said this would lead to delays in processing asylum claims.
"It is important that we recognise this is a significant judgment ... it has significant ramifications," he told reporters in Sydney.
But Mr Bowen insisted regional processing and mandatory detention would continue because they had not been found to be unconstitutional.
He also promised to make recommendations to his cabinet colleagues based on the court decision.
Opposition frets over costs, false claims
Opposition immigration spokesman Scott Morrison said the ruling would lead to taxpayers funding the legal defences of unsuccessful asylum seekers.
"What this outcome will produce is just seeing more people coming on boats with false claims, making those claims, and appealing them endlessly through the courts costing taxpayers an enormous amount of money and compromising the integrity of our immigration system overall," he told Sky News.
But Acting Prime Minister Chris Evans, who was immigration minister when the two men made their claims, rejected that assertion.
"I don't think that's going to be a huge issue," he told reporters in Perth.
In a unanimous decision, the High Court ruled that Tamil asylum seekers, who arrived by boat in 2009, were denied procedural fairness.
It considered the absence of an Australian court decision to be an "error of law".
The High Court upheld the men's appeals, based on Senator Evans failing to personally consider their cases.
Under the Migration Act, a minister can grant a visa to an asylum seeker.
Advocates call for end to system
Amnesty International refugee co-ordinator Graham Thom said the decision would still leave the immigration minister with the power to overturn court decisions that upheld asylum appeals.
"There are still a number of things the government might do," he told AAP.
The executive director of the Refugee Immigration Legal Centre, David Manne, said the High Court had found the Howard government's 2001 border protection laws to be flawed and called on Labor to respect the ruling.
The Australian Greens have called on the government to make swift changes to the Migration Act and scrap plans for a regional processing centre at East Timor.
Labor continued to deny asylum seekers the legal right to appeal when it scrapped temporary protection visas and the Pacific solution, which saw asylum seekers shipped to Nauru.
Stephen Banks, a lawyer with the New South Wales Council for Civil Liberties, said the High Court decision was likely to affect people whose asylum applications were rejected by non-statutory refugee status boards established by the Rudd government.
