Delhi Assembly Speaker Ram Niwas Goel Thursday served a notice on BJP MLA Manjinder Singh Sirsa for his "defamatory" tweets.
Goel has sought a written apology within seven days failing which he would go ahead with legal proceedings, including prosecution for criminal defamation.
Sirsa had recently claimed on Twitter that a car which displayed "Son of MLA" belonged to the speaker's son.
"The car does not belong to my client's son. The false and defamatory allegations and statements have damaged the reputation of my client," according to the notice, sent by an advocate on behalf of the speaker.