The push for a trial release of Tasmanian devils on the Australian mainland is gathering momentum with scientists and conservationists saying it would safeguard the species' survival and restore ecological balance.

Since devils on the island state were devastated by a fatal, contagious and incurable cancer, the Save the Tasmanian Devil Program has been building an insurance population and developing a vaccine.

But ecologists and conservationists say releasing healthy devils into forests on the mainland, where they were once abundant, would be of benefit to both the iconic marsupial and the ecosystem.

"Tasmanian devils are facing extinction in Tasmania," said Tim Faulkner, general manager of the conservation project Devil Ark. "In the last 20 years, 90 per cent of the population has gone. They're down somewhere now in the tens of thousands."

The Devil Ark, at Barrington Tops in the NSW Hunter Valley, has 165 healthy devils in its captive breeding program. Mr Faulkner, this year's Australian Geographic conservationist of the year, said releasing up to 30 sterilised devils in the area could reduce fox and feral cat numbers, protecting native fauna. He said the only resistance came from the Tasmanian government, which must approve any mainland release.

"In fairness they see the devil as ... [part of their] cultural identity, state identity," he said. "But we need to chop down state boundaries, move past that. The bottom line is that Australia doesn't lose any more of its wildlife."

Since European settlement, 29 Australian mammal species have become extinct. Numbers of feral cats and foxes exploded after dingoes were culled in the country's south-east to protect livestock.

Ecologists at the University of New South Wales modelled the likely impact of reintroducing Tasmanian devils to south-eastern NSW, finding the carnivorous scavenger would deter cats and foxes.

Chris Dickman, Professor in ecology at the University of Sydney, said Australia was "in desperate straits from fox and cat predation" and reintroducing devils would restore "a vitally important ecological service to the mainland. If we care anything about our natural heritage, I think we've got to do it."

Professor of wildlife conservation at the University of Tasmania, Chris Johnson, said devils were once widespread in south-east Australia.

"It's not as if we're introducing the cane toad," he said. "It will be a kind of homecoming."

He said it couldn't hurt to have devils on the mainland. "It would mean we had more devils over larger areas ... [and less] likelihood of them going extinct because of some catastrophic event. We wouldn't have all our eggs in one basket".

In the fight against Devil Facial Tumour Disease, the Save the Tasmanian Devil Program aims to maintain the insurance population of more than 600, establish disease-free wild populations in Tasmania, monitor wild devils and manage diseased populations.

It is trialling immunisation viability, with 20 vaccinated devils recently released in the state's north. Four have so far been hit by cars.

Conservation charity Rewilding Australia is petitioning Tasmanian Environment Minister Matthew Groom to discuss a trial mainland release.

"Disease-free wild devils will always be needed to maintain any captive population's genetic integrity,"  the charity's founder Rob Brewster said. "If something happens to the remnant wild population in Tasmania and we can no longer draw from it, that will be the end of the devil."

Mr Groom said the insurance population was big enough to start trial reintroductions to the Tasmanian landscape "and this is where the focus will remain" for now.

"At this stage the focus of the conservation effort for the Tasmanian devil is ensuring its survival in the wild in Tasmania," he said.