The incident took place last night around 9.30 pm when Parrikar was canvassing for local candidate Mahadeo Shirodkar who is pitted against Goa Pradesh Congress Committee president Subhash Shirodkar in the constituency.
Police said the worker identified as Dinesh Nanda Shirodkar was grievously injured after a stone hit him on his head following which he was shifted to a nearby hospital.
According to eye witnesses,a crowd of around 600 people was present for the meeting.
BJP supporters later reached the Ponda police station demanding action against the suspects and a complaint was filed against three of them — Govind Shantaram Naik,Imran Shaikh and Sirajuddin Bhat.
Police are on look out for the accused.
Goa is going to polls on March 3.