The Government should consider targeted air strikes against Islamic State militants, a former First Sea Lord said.
Lord West, now a member of the National Security Strategy Committee, said the option of air strikes "should be on the table" following the threat to kill a British hostage.
He said the militants responsible for the deaths of James Foley and Steven Sotloff were effectively "dead men walking".
I've been told at the Nato summit that the intelligence services know exactly who 'Jihadi John' is - or at least are 99.9% certain.
The British aid worker being held by Islamic State is David Haines, a 44-year-old father-of-two from Perth, Scotland.
In a video statement which claims to record his final words US hostage and journalist Steven Sotloff blames US foreign policy for his death.