The immigration minister, Chris Evans, says allowing in unskilled temporary workers to help manage Australia's labour shortage is up for debate.
It could be a modelled on a similar scheme operating in New Zealand, and could attract workers from the Pacific.
New South Wales Senator-elect Doug Cameron, a former national secretary of the Australian Manufacturing Workers' Union, says Australia should not have a two-tiered immigration system.
He says experiences overseas shows guest workers push down wages and conditions for all workers.
"I don't think this can simply be an economic analysis, this has to deal with the social consequences of what you do as well," he said.
"Overseas - in the UK, the US, Europe and in Asia - problems with migration schemes are there and we just can't sweep it under the carpet".
But the national secretary of the Australian Workers Union, Paul Howes, has told Radio Australia's Pacific Beat program the union has given its in-principle support.
"We'll support a program, as long as it ensures that Pacific islanders working in Australia will not earn one dollar less than an Australian worker doing the same work would earn," he said.
"And secondly, there are enough safeguards and measures put in place to ensure there isn't any exploitation of Pacific islanders working in Australia".
The opposition leader, Brendon Nelson, says he does not support a proposed unskilled guest worker scheme.