The Australian opposition Greens are worried a nine-year-old asylum seeker who arrived on a Torres Strait island on Sunday will be put in an offshore detention centre.
The boy and his parents were found on Saibai Island, an Australian island just off the coastline of Papua New Guinea.
They told immigration officials they were from Afghanistan.
Greens senator, Kerry Nettle, says Australia can and should process their claims on the mainland.
Ms Nettle says sending the child to Nauru would represent the reintroduction of the policy of locking up children.
She says it would also be a betrayal of the deal done with Coalition backbenchers last year to end this cruel practice.