Temporary protection visas could be scuttled in the Senate if Labor sides with the Australian Greens.
The upper house on Wednesday will consider a Greens disallowance motion that will quash the Abbott government's reintroduction of the visas.
Greens Senator Sarah Hanson-Young says the visas, used during the Howard government years, are "senselessly harsh".
They gave refugees protection for up to three years and banned them from applying for permanent protection.
Labor abolished the visas in August 2008.
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A Greens spokesman later told AAP the disallowance motion will be postponed until early December because the opposition wants more time to consider its position.
