A day after the CBI gave him a clean chit in the Vyapam scam case, Madhya Pradesh Chief Minister Shivraj Singh Chouhan slammed the opposition for levelling "false" allegations and said he was clean.Speaking to reporters on the sidelines of a function to observe the state's foundation day on Wednesday, Chouhan said: "People working in public life should not level false allegations against an opponent, just for the sake of defaming them. It is not good for politics."Asked about his name not being included in the CBI chargesheet, he said, "The opposition has a right to level allegations but those allegation must be based on facts."He added: "I was clean, so a clean chit to me was obvious."Former Chief Minister Digvijay Singh had moved a writ petition in the Supreme Court seeking investigation of a hard disk relating to the Vyapam scam case. There was also a pen drive. As per the Supreme Court order, the CBI also sent seized documents including a hard disk to Hyderabad Forensic Science Laboratory for examination.The CBI on Tuesday filed a charge sheet against 490 persons in the multi-crore Vyapam examination scam that broke out in Madhya Pradesh in 2013, while giving a clean chit to Chief Minister Shivraj Singh Chouhan. The Central Bureau of Investigation (CBI), while submitting the charge sheet in the Special Court in Bhopal, told the judge that there was no tampering with a hard disk drive seized by the Madhya Pradesh Police in the case, dismissing an allegation by senior Congress leader and former Chief Minister Digvijaya Singh on this count.