Afghanistan has plunged into its worst humanitarian crisis since the start of operations in 2001 after American and British forces pulled out 18 months ago, the outgoing head of the international Red Cross has said.

The drawdown of Nato troops including the British and Americans has seen an upsurge in fighting, with the Taliban now able to bring the war to major cities for the first time, Jean-Nicolas Marti told The Telegraph.

Last year saw the number of war wounded evacuated by the International Committee of the Red Cross grow by 30 per cent on the year before. This year’s figure is already on course to outstrip that, even before the summer “fighting season” starts.