(AFP)- US President President Barack Obama should resign if it can be shown that he approved spying by US diplomatic figures on UN officials, the founder of WikiLeaks said in an interview published today. The whole chain of command who was aware of this order, and approved it, must resign if the US is to be seen to be a credible nation that obeys the rule of law. The order is so serious it may well have been put to the president for approval, Julian Assange told the Spanish daily El Pais. Obama must answer what he knew about this illegal order and when. If he refuses to answer or there is evidence he approved of these actions, he must resign, he added during an internet chat interview published online. WikiLeaks threw US diplomacy into chaos when it started releasing more than 250,000 classified State Department cables on November 28, creating an international firestorm as American diplomats private assessments of foreign leaders and politics have been publicly aired.