The Indian government is investigating allegations that a former close confidant of opposition prime ministerial candidate Narendra Modi had ordered police illegally to spy on a woman on behalf of his "boss". The move to investigate the alleged 2009 surveillance just months before general elections came as a court, in a major boost to Modi, rejected a petition to prosecute him over his role in 2002 religious riots that left 2,000 people dead. "The cabinet has approved a proposal to set up a commission of inquiry … to look into the incidents of physical/electronic surveillance in the states of Gujarat and Himachal Pradesh, and the national capital territory of Delhi, allegedly without authorisation," a government statement said. The decision provoked outrage from Modi's Hindu nationalist Bharatiya Janata Party (BJP), which labelled the investigation as a "witch-hunt". Modi, the chief minister of Gujarat state since 2001 and now a prime ministerial candidate, is leading in opinion polls, well ahead of the ruling Congress party, just months before elections due by May. Modi has been studiously crafting his image as a pro-business reformer who can revive India's flagging economy as head of a corruption-free, efficient government. But the allegations, contained in 267 audio recordings released to two investigative websites last month, could damage that reputation. The websites said the recordings included telephone conversations in which Modi's former junior home minister in Gujarat ordered a police officer to track the woman. In the phone calls, the minister purportedly asked the surveillance to be carried out for his "saheb", a respectful Hindi word for "boss". Modi was not named. Gujarat police then allegedly used their powers to tail the woman as she visited shopping malls, the gym and even her ailing mother in hospital. Last month Modi's Gujarat government ordered its own investigation into the allegations, which the Indian media have dubbed "snoopgate". The BJP has attacked the inquiry ordered by the Congress-led federal government, and are calling it a "clear case of political vindictiveness" and "a witch-hunt". "Clearly it is the fascist Congress... that has taken such a decision. (The) BJP shall meet all the challenges and fight at every platform," BJP spokeswoman Nirmala Sitharaman said.