Addressing the Chatham House foreign affairs think tank, Scheffer said the allied forces could not afford to lose the war on terror in Afghanistan, as it would then give a free run to al-Qaeda's global terrorist ambitions.
Scheffer, who will step down from his post next week, expressed fears that if Afghanistan falls into the Taliban's hands once again, it would have catastrophic effects.
"If we were to walk away, Afghanistan would fall to the Taliban, with devastating effect for the people there, women in particular," The Telegraph quoted Scheffer, as saying.
"If one reads any national press, you could be forgiven for thinking that your forces were fighting in Afghanistan alone. But they are not. They are part of a team. 14 nations are fighting in the south of Afghanistan, alongside their British colleagues, along with Afghan forces," he said.
Scheffer said there should not be any question over the 'necessity' or the 'legitimacy' of the international forces' operation in Afghanistan.