"He travelled here under his own free will. He has told us that he is resigning his post," it added.
"Mussa Kussa is one of the most senior figures in Qadhafi's government and his role was to represent the regime internationally, something that he is no longer willing to do," the British statement continued.
"We encourage those around Qadhafi to abandon him and embrace a better future for Libya that allows political transition and real reform that meets the aspirations of the Libyan people," it concluded. Kussa had arrived after a two-day stay in Tunisia, which Tripoli had officially described as a "private visit." He entered Tunisia on Monday via the Ras Jdir overland border crossing. His departure is just the latest blow to the Tripoli regime. Several senior members of Qadhafi's entourage, including ministers and senior military officers, have defected since the uprising against his 42-year-rule began more than a month ago. Washington quickly hailed Kussa's departure as a major blow to the Qadhafi regime.
"This is a very significant defection and an indication that people around Qadhafi think the writing's on the wall," a senior official in the US administration said. Kussa is credited as having been a key figure in Libya's efforts to improve its international reputation before to the current crisis. News of his arrival came just hours after British Foreign Secretary William Hague announced that London was expelling five Libyan diplomats, including the country's military attache. They were being kicked out for having intimidated Libyan opposition groups in London, Hague told Parliament.
"The government also judged that were these individuals to remain in Britain they could pose a threat to our security," he added. In Libya itself meanwhile, the rebel forces suffered a serious reverse. Their forces were driven back some 200 kilometres by the superior firepower of Qadhafi's forces in a chaotic stampede that saw them yield most of the ground their recent advances had secured.