Galbraith was fired in October as the U.N. deputy special envoy to Afghanistan by Secretary-General Ban Ki-moon following disputes over the transparency and credibility of the presidential elections.
Afghan election officials handed incumbent President Hamid Karzai a victory when former Foreign Minister Abdullah Abdullah, his closest challenger, pulled out of a runoff vote ordered because of fraud in the Aug. 20 contest.
Galbraith, writing in London's Independent, notes the election fraud has "shaken the confidence" of NATO in Afghanistan and "undermined the U.N.'s credibility in that country."
His comments come as world leaders deliberate over the best way forward in the war effort in Afghanistan. Several leaders have come forward recently saying their level of support for Afghanistan depended on the legitimacy of the Karzai government.
U.S. President Barack Obama ordered his top military generals to come up with new options for the war strategy after deliberating over a series of measures during war council meetings Wednesday.
Government corruption, London's Telegraph reports, prompted Gen. Karl Eikenberry, the former top military commander in Afghanistan, to tell the U.S. president that increasing the troop strength in Afghanistan was "not a good idea."