Foreign Secretary Philip Hammond said the Islamic State is “turning a swathe of Iraq and Syria into a terrorist state as a base for launching attacks on the West."
Writing in The Sunday Times (£)he said: unless the jihadists are stopped “sooner or later they will seek to strike us on British soil."
The death of US journalist James Foley is a reminder that Islamic extremism is a barbaric ideology that is threatening us at home, he said.
He added: "It is horrifying to think that the perpetrator of this heinous act could have been brought up in Britain."
A British family have told ITV News of their devastation after discovering a close relative is fighting with the Islamic State in Iraq.
A French journalist who was held hostage with James Foley in Syria has told ITV News it was "devastating" to see his murder.