In an open letter to Kejriwal, Bhushan said "God and history will not forgive what you are doing to the party,"
Bhushan and Yadav were expelled from AAP's National Executive on March 28 for "anti-party activities".
"After winning the Delhi elections with such a thumping majority, when you have such good fortune, you should be showing your best qualities to the people of this country. But unfortunately, your worst qualities have emerged now," Bhushan said.
The party founded with a dream of "clean and principled" politics may well turn into a "nightmare", he said.
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Bhushan also said it would be wrong on Kejriwal's party to think that people will forget about the "betrayal" if he delivered on good governance.
Bhushan said "the fear that I have, is that after how you have behaved and the character traits that you have showed, this dream of clean and principled politics that the Aam Aadmi party was founded on may well turn into a nightmare".