WASHINGTON (AFP) - The office that oversees billions in aid to Afghanistan will be without a chief for the second time this year, as its leader announced Thursday he was stepping down. Herbert Richardson, acting special inspector general for Afghanistan reconstruction (SIGAR), said he will take a job in the private sector after he leaves his government post on September 2. After more than 37 years of public service, Ive decided to accept an opportunity in the private sector at a time when Im convinced SIGAR has changed course, is producing results and is being led effectively by the new leadership team that Ive put in place, said Richardson. Created by Congress, SIGAR is tasked with investigating and leading audits of the more than $62 billion in aid distributed by the United States to Afghanistan since 2002. The organisations previous manager was dismissed in January after lawmakers criticised SIGAR for failing to properly uncover misuse of the aid money. A SIGAR report published last month revealed that funds Washington poured into Afghanistan for aid could be financing corruption and going to extremist groups because the money was not traceable. Richardson stepped down as a new report by the International Crisis Group (ICG) think tank highlighted major problems over foreign aid in Afghanistan, which it said has totalled $57 billion since the US-led invasion in 2001. Ahead of a deadline for the withdrawal of overseas combat troops by the end of 2014, the ICG warned Afghan state bodies remain weak, including the countrys army and police which have received over half the total aid. The impact of international assistance will remain limited unless donor countries take swift action, it added. It urged countries - particularly the United States, the largest aid donor to Afghanistan - to tackle corruption, better monitor how aid is implemented and separate aid from counter-insurgency goals.