ISLAMABAD- The Pakistan Tehreek-e-Insaf chairman Imran Khan today reiterating his stance said that transparent investigation into general election vote fraud is not possible with Nawaz Sharif in the office of the prime minister. "We cannot trust NS with investigation on rigging. Once we leave & pressure is off, he will do everything to sabotage investigation process," Imran Khan said in a message posted on micro-blogging site. The PTI chief claimed that past record of Sharif brothers shows that they bought or scared witnesses. He alleged that Shahbaz Sharif is already sabotaging the Model Town tragedy's first information report (FIR).