General Sir David Richards, the Chief of General Staff, said that contingency plans for military intervention are being "continually brushed over" as Syria's civil war continues.

He stressed that any troop involvement would be limited and conditional on the support of people in the affected area, but his remarks raise the spectre of the UK being involved in another conflict at a time when the West is trying to extract itself from the 11-year war in Afghanistan.

General Richards told BBC1's Andrew Marr programme that the UK's main concern is preventing the Syrian civil war from spilling across borders into Jordan, Lebanon, or especially Turkey, a Nato ally.