The FIR was registered against MLA Ram Kadam and 15 others after a mob barged into the office of Brihanmumbai Municipal Corporation's Deputy Engineer Mahesh Fad (36) at Ghatkopar on Thursday, police said.
The alleged assault on Fad was after he had overseen the demolition of an illegal two-storey house in Bhatwadi, Ghatkopar (East).
Later, the officer was allegedly threatened by Kadam, who asked him not to go ahead with the drive, police said.
However, the engineer continued with the demolition and after a while, a group of people, including a woman, Mangal Kamble, whose structure was demolished, threatened the engineer and threw water bottles and punching machine at him, police said.
The engineer, who was injured in the attack, approached the police station on Thursday evening, said Suresh Nirmal, Senior Inspector at Pant Nagar police station.
Nobody has been arrested so far; police said adding that investigations were on.
The legislator and others were booked under IPC sections 141 (Unlawful assembly), 147 (Punishment for rioting), 353 (Assault or criminal force to deter public servant from discharge of his duty), 332 (Voluntarily causing hurt to deter public servant from his duty), 336 (Act endangering life or personal safety of others), 452 (House-trespass alter preparation for hurt, assault or wrongful restraint), 504 (Intentional insult with intent to provoke breach of the peace) and 506 (Punishment for criminal intimidation), among others.