Iraq crisis: Cameron warns of possible IS threat to UK
17 August 2014 Last updated at 22:26 BST
Islamic State militants could grow strong enough to target people on the streets of Britain unless action is taken, David Cameron has warned.
The PM, writing in the Sunday Telegraph, said a "humanitarian response" to IS was not enough and a "firm security response" was needed.
It came as Church leaders expressed concern that the UK had no "coherent" approach to tackling Islamic extremism.
BBC political correspondent Iain Watson reports.