"Instead of calling me a 'weather man', Prasad should explain as to why he had to join forces with senior JD(U) leader Nitish Kumar whom he had been denouncing with choicest words for past 20 years," he told reporters here.
His remarks came after Prasad dubbed him as a "weather man", accusing him of "changing tack to suit his own political requirements without carrying a baggage of ideology".
At a rally in Chapra addressed earlier in the day by RJD, JD(U) and Congress for an Assembly bye-election, Prasad said, "He (Paswan) is a rank opportunist who switches sides at the drop of a hat."
Hours later, an angry Paswan cautioned Prasad to refrain from passing "below the belt" remarks against him.
"If I have been a weather man, what is he as he joined hands with Nitish Kumar after attacking him for 20 years," he asked before leaving for Hajipur to campaign for BJP.
During campaigning for the bypolls in ten Assembly seats, Prasad has been ridiculing the LJP leader as a "habitual turncoat" and a "weather man".
BJP candidate Awadesh Kumar is contesting from Hajipur, a seat vacated by BJP MP Nityanand Rai on being elected to Lok Sabha.