The Prime Minister has argued the biggest danger facing this country is British-born jihadists returning to the UK; it is thought around 400 are in Syria with an unknown number in Iraq.
During Commons Question-Time, he told MPs the UK Government's approach would be "long-term, hard-headed, patient and intelligent", stressing that it was important Nouri al Maliki, the Iraqi Prime Minister, tackled extremism in his country, pushed back the Isis terrorists from the territory they had gained, closed down ungoverned space, and that the Baghdad government must represent the interests of all the people of Iraq, not just the Shia majority.
Mr Cameron then insisted: "I disagree with those people who think this is nothing to do with us and if they want to have some sort of extreme Islamist regime in the middle of Iraq, that won't affect us; it will. The people in that regime, as well as trying to take territory, are also planning to attack us here at home in the UK."
He announced Britain was increasing the humanitarian aid it was sending to people displaced by fighting in Iraq from £3 million to £5 million.
After the PM chaired a meeting of the National Security Council, which is made up of ministers, officials and defence and intelligence chiefs, Downing Street stressed how the Coalition would continue to do all it could to address the threat posed by jihadists returning to the UK.
This would involve "interviewing individuals at the UK border suspected of being involved in acts of terrorism, cancelling or withdrawing passports of suspected foreign fighters seeking to travel to Syria or Iraq, and introducing new measures to prosecute those who plan and train for terrorism abroad".
A No 10 spokesman explained the NSC meeting had concluded "we should press the Iraqi Government to pursue an inclusive political response and that we should work with moderate Shias, Sunnis and Kurds in Iraq who support a democratic, pluralistic state with respect for the rule of law".
He stressed UK military intervention was not on the table but Britain should continue to work with the US and Gulf states to prevent the spread of violent extremism. "We should continue to provide humanitarian support to Iraq and neighbouring countries bearing the burden of refugees fleeing Iraq and Syria," he added.