The Australian Greens are proposing their own Migration Act amendments to affirm onshore processing of asylum seekers.
They also are calling on Labor and Liberal backbenchers to cross the floor of parliament to support them.
The government on Wednesday introduced draft laws aimed at resurrecting its controversial Malaysian people swap deal by restoring the government's power to send asylum seekers to third countries, placed in doubt by the High Court last month.
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The government's legislation is expected to be defeated because the coalition and Greens both oppose it. An alternative coalition proposal is also set for defeat.
Nonetheless, the Greens will seek to amend the government's proposal by stripping it bare and replacing it with a statement of support for onshore processing.
"I'm hopeful that not only some of the other members of the crossbench might support it but that those members of parliament from both sides who have spoken out against offshore processing will take this opportunity to come and support our amendment," Greens MP Adam Bandt said.
Greens immigration spokeswoman Sarah Hanson-Young said the asylum seeker debate was increasingly ugly.
"A race to the bottom between the sellouts and the hypocrites, between Julia Gillard and Tony Abbott trying to prove who can be the toughest, the meanest, the nastiest," she said.
