Tony Abbott believes Australia needs special terror courts to deal with returning foreign fighters.
The former prime minister says the only safe jihadi is one who has been lawfully killed, imprisoned or thoroughly converted from Islamism.
"We need to ensure every returning jihadi can readily be charged and convicted, possibly through the creation of special courts that can hear evidence that may not normally be admissible," he writes in News Corp publications on Thursday.
Deputy Prime Minister Barnaby Joyce said it was a matter for the attorney-general, but noted Australia had very strong anti-terrorism laws and offenders suffered the consequences.
"If you want to go overseas and murder other people, well you're an evil person and if what you really want to do is be involved in conflict, join the Australian Army and do it legally," he told reporters in Canberra.
Labor frontbencher Chris Bowen said Mr Abbott's comments were more about Liberal internal politics than a serious discussion of matters facing Australia.
Labor MP Tim Hammond agreed, saying Mr Abbott's remarks were a sign of discord between the prime minister and the Liberal Party's conservative right.
"What it confirms is what we've known all along and that is the real government here is not Malcolm Turnbull," he told reporters.
