Siddiqui's personal secretary Shyam Bihari Dixit filed a police complaint at Hazartganj police station last night alleging that an unidentified person called his staff and asked for the former minister, police said today.
However, when the staff member informed the caller that the leader was busy he used abusive language, police said.
Later, he again made a call and when Siddiqui received it, he allegedly threatened him of dire consequences, they said.