Basirhat North MLA A T M Abdullah was assaulted when he was leading the procession, police said, adding he was allegedly attacked with bamboo poles and bricks.
He was rushed to Dhanyakuri hospital where medical examination was underway.
The MLA blamed CPI(M) supporters for the attack.
Meanwhile, Trinamool Congress workers have put up a road blockade at Dhanyakuri.
Results of the state Assembly elections were declared on May 19.