Video: David Cameron addresses Australian parliament on fight against jihadists Britain and Australia have both sent their militaries to fight in a US-led coalition against Islamic State extremists in northern Iraq. They have also both had radicalised citizens leave to join terrorists fighting in both Iraq and Syria. David Cameron told the Australian Parliament the root cause of extremism was not poverty or social isolation but the extremist narrative. The prime minister briefly outlined proposed legislation in Britain aimed at preventing militant suspects from travelling, including cancelling their passports while they were overseas and defended a measure that would prevent such suspects from returning to Britain. "Successive governments have come to the view - and I agree with the view - that when you're facing an existential challenge as great as the one we face with these Islamist extremists, you need additional powers as well as simply the criminal law," Mr Cameron told reporters. Mr Cameron's visit to Canberra comes ahead of his attendance at the G20 summit of leaders of wealthy and developing countries in the east coast city of Brisbane at the weekend.