Malcolm Turnbull has labelled Syria's leader a "murderous tyrant" while Bill Shorten says peace in the conflict-torn country isn't possible as long as "the butcher Assad" remains in power.
But the prime minister insists there needs to be a pragmatic solution to the Syrian issue despite very deep enmities towards President Bashar al-Assad and his brutal regime.
"The key to a political settlement in Syria is finding a mechanism where the aggrieved Sunni majority of that country can ... be included in a new government".
And it's a solution that doesn't include Islamic State.
"The key to a political settlement in Syria is finding a mechanism where the aggrieved Sunni majority of that country can ... be included in a new government," Mr Turnbull told reporters in Manila on Thursday where he is attending the APEC summit.
If that could be achieved IS would lose its fundamental base, he said.
Labor leader Bill Shorten says leaving the Assad regime in charge gave no prospect of long-term stability to millions of people in Syria or those wanting to return to the country.
"There can be no lasting peace if you keep the butcher Assad in power," he told reporters in Sydney.
Asked if he agreed to the "butcher" label, Mr Turnbull said: "I think he has been a murderous tyrant, there is no doubt about that."
Earlier Liberal Senator Zed Seselja acknowledged air strikes against IS targets in Syria had not made the kind of impact Australia had hoped for, raising the option of combat troops.
Fellow Liberal Dan Tehan, who is chairman of parliament's intelligence and security committee, believes a political solution could be achieved in Syria within six months.
Mr Tehan said President Assad and his chemical weapons should be taken "out of the picture".
"What we need to do is show that we have the will to act and to act quickly and decisively against Islamic State," he told ABC radio. Mr Tehan refused to be drawn on whether Australian SAS troops should be sent into Syria to advise rebels, but said more military force would be needed.
