The federal government is breaching its own policy against holding asylum-seeker children behind wire, according to Greens leader Christine Milne.

About 125 unaccompanied boys have been transferred from other Australian immigration facilities to the secure Pontville centre, on a rural plain outside Hobart.

Around 125 unaccompanied boys have been transferred from other Australian immigration facilities to the secure Pontville centre in Tasmasnia. Credit:Alastair Bett

A spokeswoman for the outgoing Immigration Minister, Chris Bowen, told Fairfax on Friday: ''Children in detention are never kept 'behind wire' under this government.''

But Ms Milne said she visited Pontville, and found the boys were behind high fences.