In an address to the Lowy Institute, Curtin University's Anne Aly said the strategy was fraught with danger, not only in selecting the right candidates but also in constructing the narrative itself.

"I don't believe in directly engaging with Daesh or Islamic State because that's what they want," Dr Aly said."They want to draw you into a discussion … they want you to challenge them so they can tell you what they are all about.

"How do you counter that narrative? You counter that narrative by creating your own game … don't play their game.

"You look at who they are targeting and you target them with something completely different, and better, and more attractive and more influential."

Speaking later to Fairfax Media, Dr Aly said trying to combat extremist groups by challenging the 'facts' they espouse or, in the case of Islamic State, the extracts from the Koran they cite for killing 'infidels' and enslaving women "really hasn't worked".

An effective counter narrative would have to differ for each individual but could mean addressing a person's propensity for violence or deploying anger management techniques to would-be jihadists, she said.

The federal government is currently weighing a bid from numerous Australians who travelled to the Middle East to join with Islamic State and had their passports cancelled, but now want to return home.

Some, including Melbourne man Adam Brookman, have pledged to advocate to stop others going to join Islamic State if they are allowed to return, suggesting the new role should encourage authorities and the courts to show leniency towards them.

Dr Aly said returnees had to be carefully assessed on a case by case basis. Many left because they were disillusioned with the theatre of war or with Islamic State itself but still retained extremist views.

"They haven't become disillusioned and done a 180. They will wait for another group, or another theatre or another opportunity."

While there were relatively rare examples of people who jettison the ideology entirely, the best prospects for anti-jihad spokespeople were the growing number of young people, many teenagers, who were heading to the Middle East, she said.

"There are kids who go over there who are drawn by the violence, drawn by the action and then get put in an orientation camp and go 'Mama, what have I done!'," she said.

"There's a case for really looking at those particular cases of the young people who are neither ideologically nor behaviourally radicalised but are attracted by the violence and have gone there and gone 'I have made a huge mistake'."

It was poorly appreciated that many "self-radicalisers" already had a propensity to violence, Dr Aly said.

Melbourne teenage suicide bomber Jake Bilardi was a classic case. Along with a variety of Islamist groups, he was fascinated by ultra-violent Mexican drug gangs.

"His main driver was the violence itself. the need to carry out an act of violence. At one point in his thought process, he says to himself: 'Well, if I'm going to do this, I guess I better become a Muslim'," she said.

"He had already determined that he wanted to fight, that he wanted to undertake an act of violence. He came to the ideology only after that ... in order to frame that violence somehow."