"The nation wants to know what magical model does Robert Vadra have so Rs.1 lakh becomes Rs.300 crore in less than three years," Prasad said at a press conference in the state capital.
He also accused Priyanka of jumping into this mud-slinging after her brother and Congress vice-president Rahul Gandhi and mother Sonia Gandhi failed to take on Modi.
At a time when investment in the country is going down, there needs to be some explaining on how Robert Vadra's companies are flourishing, the BJP leader said.
Read: Priyanka asks Modi to stop 'lessons', says he 'gave thousands of acres of land to friends'
Prasad pointed out that Congress governments in Rajasthan and Haryana flouted all norms and bended backwards to accommodate and promote the business interests of Vadra. He also charged the Congress of victimising honest officials like Ashok Khemka.
Responding to a question on media reports that the Congress had come out with a sub-manifesto promising 4.5% quota to backward Muslims, Prasad said the move was politically unethical and unconstitutional.
"Interests of the Other Backward Classes would be compromised if such a move takes off," he said.
Prasad questioned the silence of leaders like Samajwadi Party chief Mulayam Singh Yadav, Rashtriya Janata Dal president Lalu Prasad, Bahujan Samaj Party supremo Mayawati, and Bihar CM Nitish Kumar, on the contentious issue.