The government's decision to suspend immigration claims of Sri Lankan and Afghan asylum seekers is likely to mean people are detained indefinitely for years, refugee advocates say.
The opposition has accused the government of being more concerned with winning the next election than stopping the arrival of boats, while the Australian Greens have described it as a "redneck" solution.
Other critics say the changes are reminiscent of the previous Howard government's policies to suspend the processing of Iraqi and Iranian asylum seeker claims.
Immigration Minister Chris Evans says the government will review the situation in Sri Lanka after a period of three months and in Afghanistan after six months.
The government will continue processing claims from those already on Christmas Island or on the way there.
But Refugee Action Coalition spokesman Ian Rintoul said the politically-driven policy change was more likely to see asylum seekers detained for a "long period of time" rather than returned to their home countries.
'No solution' to people smuggling
"They're going to sit in detention having committed no crime," he said. "Having justifiably fled persecution, the government refuses to process them, only see them rot in detention."
In 2003, the Howard government suspended indefinitely the immigration claims of Iraqi asylum seekers after US-led forces overthrew dictator Saddam Hussein.
Mr Rintoul said this policy led to some Iraqis being detained in Australia for more than three years, before their next review, because they could not be sent back to their country of origin.
The Howard government also suspended the immigration claims of Iranian asylum seekers in 2001 but the policy was softened in 2004 when then immigration minister Amanda Vanstone allowed temporary protection visa holders to apply for mainstream visas.
Mr Rintoul said the Rudd government's changes would compromise the integrity of immigration processing and take away the ability of officials to assess the personal experiences of claimants.
"It's disgraceful, unjustified and totally unnecessary," he said.
Opposition immigration spokesman Scott Morrison says the government's solution to the rising number of boat arrivals will not solve the problem of people smuggling.
Asylum changes 'totally inhumane'
"The government basically has a plan for the election not a plan for the boats," he said.
"This is a cynical political announcement rather than addressing what the UN has described as a problem."
The Australian Greens say the changes are "totally inhumane" and revive the worst aspects of the previous Howard government's asylum seeker policies.
"Detaining people indefinitely really is on a par with the inhumane and awful conditions of temporary protection visas," said immigration spokeswoman Sarah Hanson-Young.
The six-month suspension period for Sri Lankan and Afghan asylum seekers also coincides with a possible election date.
"We have what is Kevin Rudd's redneck solution in the lead-up to the election campaign," Senator Hanson-Young said. "We are in very dangerous waters."