The Election Commission on Thursday issued a show cause notice to BJP MP Parvesh Verma for allegedly calling Delhi Chief Minister Arvind Kejriwal a "terrorist".
He has been given time till 5 pm on Friday to respond.
The notice came on a day when he was barred from campaigning for 96 hours (four days) for making controversial remarks at a poll meet recently.
The EC has also ordered his removal from the BJP's list of star campaigners.
The notice said the AAP had approached the Delhi chief electoral officer with a complaint.