Aam Aadmi Party (AAP) legislator Kartar Singh Tanwar's car was attacked here on Sunday, leaving a friend injured, party leaders said.
Unidentified men staged the attack with iron rods near Katwaria Sarai area in south Delhi.
Police said the legislator, who was not injured, had filed a complaint.
"The goons attacked his vehicle and injured the friend, Ajit, " AAP leader Deepak Bajpayee told IANS.
The injured man was rushed to the All India Institute of Medical Sciences.
According to other AAP sources, the attackers escaped in their car after Tanwar's driver came out.
Tanwar is one of the 67 AAP legislators in the 70 - member Delhi assembly.