Bharatiya Janata Party (BJP), the main opposition party, on Thursday asked Congress to answer former coal secretary PC Parakh's question as to why Prime Minister Manmohan Singh should not be charged with conspiracy and corruption in the coal scam case.

PC Parakh, who along with industrialist Kumar Mangalam Birla was earlier this week charged by the Central Bureau of Investigation (CBI) with conspiracy and corruption in connection with coal blocks allocation scam, argued that why the prime minister should not be slapped with the same charges when he was the final decision maker in the process of coal blocks allocation.

Supporting the former coal secretary's views, Senior BJP leader Venkaiah Naidu said that he wanted the Congress to answer Parakh's question. He also accused the CBI of being selective in its action against wrongdoers.

In a press release on Thursday, Naidu said, "I want to know from the Congress what their reply to Parakh's question is; why is CBI selective in its action? Is it an attempt to divert attention to protect bigger fish?"

Meanwhile, Kumar Mangalam Birla's flagship firm Hindalco remained clueless about the Rs 25 crore that the CBI seized from the company's Delhi office.

The huge amount of cash was recovered during raids conducted on Tuesday after the investigative agency registered an FRI against Hindalco chief Kumar Mangalam Birla.