A Muslim cleric who preaches from certain passages of the Koran could be caught in the "broad" net of the government's new anti-terror law, Islamic leaders have warned.

Grand Mufti of Australia Ibrahim Abu Mohammad and the Australian National Imams Council have called for the offence of "advocating terrorism" to be removed from the so-called Foreign Fighters Bill, currently before Parliament.

They went public with their opposition on the same day Prime Minister Tony Abbott backed the draft legislation as essential to reining in "preachers of hate", including the radical Islamic group Hizb ut-Tahrir.

The organisation is hosting a lecture in Lakemba on Friday to denounce "the politics and plots of the American-led intervention in Iraq and Syria" and Mr Abbott has conceded that the current legal framework is not sufficient to shut the event down.The imams council said a cleric could fall foul of the new law even if he simply "advocated the duty of a Muslim to defend his land".