The Prime Minister made the comment at a youth conclave in Surat on Wednesday.
Dadlani, who often criticises the Modi-led BJP, called it a "lie".
"Lie. Name one rapist who has been hung in your term, Sir. Nirbhaya's rapists, Asifa's rapists, even Unnao child-rape-accused BJP MLA Sengar are still alive and well," he tweeted on Thursday.
"Narendra Modiji, we know elections are near, but don't turn the pain of Indian women and girls into propaganda," he added.