"Vinash Kale vipreet buddhi (taking wrong decisions when on path of destruction)," Kumar told reporters here.
Kumar, who was instrumental in his party breaking up with BJP over the issue of Modi's elevation after staying in NDA for 17 years, said the saffron party was working against opposition unity.
The country would never accept a "divisive" element, the senior JD(U) leader said.
Instead of adding new partners in the NDA, it lost a trusted friend like JD(U), Kumar added. JD(U) broke up from BJP on June 16 this year.
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Without naming veteran BJP leader L K Advani, who has been cornered within the party to elevate Narendra Modi as PM nominee, Kumar said "there is no respect for elders in BJP."
The BJP is trying to create an environment in favour of their leader but they would never succeed, he said.