RLSP, a Bihar based party, has three MPs in the Lower House and a part of the ruling NDA.
Kumar launched the attack on Kushwaha, a day after the latter dissolved the party's Bihar unit headed by the Jahanabad MP.
Kumar claimed the party's Bihar unit was to discuss major issues, including some pertaining to shoddy appointments in the organisation, prompting Kushwaha to dissolve it.
"Yesterday, I got a call from Upendra Kushwaha saying the Bihar unit has been dissolved. This has been done in a very arbitrary manner by Kushwaha and his coterie," he said.
Accusing the RLSP leadership of turning the party into a "shop", Kumar claimed people are appointed at posts without any proper background check or consultations.
"A fodder scam accused was appointed as party's Bihar president but it was undone after protests from party workers," Kumar said.
