Kapil Mishra was disqualified under Constitution's 10th Schedule, referred to as "Anti-Defection Law".
Delhi Assembly speaker Ram Niwas Goel on Friday disqualified rebel Aam Aadmi Party MLA Kapil Mishra under the anti-defection law, saying his campaigning for Bharatiya Janata Party and Prime Minister Narendra Modi in the Lok Sabha polls indicated that he has "given up the membership of his original political party".
According to an order issued by the speaker, Mr Mishra's disqualification takes effect from January 27 this year when he shared stage with Delhi BJP chief Manoj Tiwari and the then Union minister Vijay Goel against the AAP.
"His (Kapil Mishra's) various tweets, press conference, campaign etc. in favour of Narendra Modi and the BJP leave no one in doubt that the respondent (Kapil Mishra) has voluntarily given up the membership of his original political party," the order stated.
"Whether he has formally resigned from the AAP or taken the membership of the BJP formally is immaterial for a decision on his disqualification under Para 2 (1) (a) of the Tenth Schedule," it added.
Mr Mishra issued a statement after his disqualification, in which he termed the speaker's order "illegal" and "undemocratic" and said he will challenge it in the court.
The order was issued on a petition of AAP MLA Saurabh Bharadwaj seeking Mr Mishra's disqualification from the Delhi Assembly.
Mr Mishra said he was ready to sacrifice his MLA's post for campaigning for Narendra Modi not just once, but "a hundred times".
"On one side there is a patriot on the other side is tukde-tukde gang- I stood with whole Delhi. I ran the "all seven (Lok Sabha) seats for Modi" campaign recently, and (now) will run "all 60 seats for Modi" in Assembly polls," he tweeted in Hindi.
Delhi has seven Lok Sabha seats and 70 assembly constituencies.
Mr Mishra said the speaker's order will not stand the court's scrutiny even for a day.
The order said that the AAP convener and leader of legislature party Arvind Kejriwal had in a letter on July 2 stated that the party has no objection to the Karawal Nagar MLA being disqualified.
Three more rebel AAP MLAs - Anil Bajpayee, Devender Sehrawat and Sandeep Kumar - are facing the danger of disqualification on Saurabh Bharadwaj's petition.