"I have faxed my resignation from the post of vice-president of LJP," Khan, MLA of Araria, told PTI.
Khan said he has put in the papers in protest against the party going along with 'communal' BJP in the Lok Sabha polls.
He said he had made his position clear to Paswan that he cannot be part of any alliance with BJP and had expressed his reservation against going with it before LJP parliamentary board.
After the 2010 Assembly elections, two out of three LJP MLAs had quit the party and joined Nitish Kumar's bandwagon. Zakir Hussain Khan was the lone party MLA left.
LJP national general secretary Vijendra Chaudhary has also expressed strong reservation against any tie-up with BJP.