Under the directive, those who pay people-smugglers to arrive on unauthorised boats will be sent to the poor Pacific nation for processing and resettled there even if found to be genuine refugees.
"On the question of asylum-seekers... We've had to adjust our policy over time and I make absolutely no apology whatsoever for our current policy settings because the world around us has changed," Rudd told Channel Ten.
Rudd, who was last month reinstalled as prime minister by his Labor colleagues to help turn around dire polls in an election year, had previously softened some of the former conservative government's policies.
The plan has worried the United Nations refugee agency which said Friday that conditions at Papua New Guinea's Manus Island facility currently failed to adequately protect refugees.
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"UNHCR is troubled by the current absence of adequate protection standards and safeguards for asylum-seekers and refugees in Papua New Guinea," it said in its first assessment of the policy.
Australia resumed sending asylum-seekers to Manus Island and the Pacific state of Nauru in 2012 in a bid to deter record numbers of migrants arriving by boat, hundreds of whom drowned en route.
"It is the implementation of that policy direction over time, resolutely, which will yield results," he told Network Ten's Bolt Report.
"In the interim, people smugglers will test your resolve."
Asylum-seekers are a sensitive issue in Australia, and one set to feature prominently in the election due this year.
Rudd said while people-smugglers, who make thousands of dollars bringing asylum-seekers to Australia, would test the government's resolve "we are not for turning".