Britain must increase spending on the Armed Forces in the face of growing threats from terrorism and states such as Russia and North Korea, the Defence Secretary has said.

In comments apparently aimed at putting pressure on the Treasury, Sir Michael Fallon said the Government should “aim to do better” than its current target of spending two per cent of GDP on the military.

His remarks came as a former senior general warned that meagre defence spending meant Britain would be reliant on American protection to defend against North Korean missiles.