Using people not open affiliated to his political party to caste scurrilous & defamatory allegations on his opponents is one of Modi's modus operandi. It makes his opponent go on the back-foot while Modi can maintain plausible denial over the allegations. The puppet who carries out the hit job gets rewarded for it or is often threatened to do it.
In this case, the puppet is Ex-Sudan Ambassador Deepak Vohra and Modi govt has used India's federal investigative agency, the CBI, to threaten him with in a case of alleged financial bungling in Indian diplomatic missions.