"Narendra Modi and BJP are merely a mask....The real power lies with Nagpur (RSS headquarters)," Prasad said after flagging off RJD Rath Yatra from his residence here.
Alleging that BJP is merely carrying the "communal agenda" of RSS, the RJD chief said that saffron party by holding political meetings at different places in the country is vitiating harmony in the society.
The RJD's Rath driven by Prasad's close confidante and former MLC Anwar Ahmad in the first phase would tour minority-dominated areas of Begusarai, Khagaria, Katihar, Purnea, Kisanganj, Araria, Madhepura, Saharsa and Supual.
Prasad also attacked Kumar saying while communal forces were increasing influence in the state, "he was sitting idle".
He alleged that Kumar allowed saffron outfits to spread its influence in Bihar.
"He (Kumar) helped RSS in organising camp at historic Gandhi maidan here," the RJD chief said.
"On request of Narendra Modi he (Kumar) as a Railway minister then did not order a probe into burning of Sabarmati Express in Gujarat," he alleged.
The RJD chief claimed that "Nitish is no factor in Bihar (in 2014 elections)."