CPM former MP Ram Chandra Dome, along with several party activists, was injured after their protest march was attacked in West Bengal's Birbhum district on Saturday.
The march was led by the Bengal Platform of Mass Organisations (BPMO), which consists of 113 Leftist organisations across the state.
The march was aimed to intensify mass contact ahead of next year's Assembly polls, and in support of a 15-point programme that includes protests against the "growing intolerance" in the country as well as "attacks on democratic rights" in the state.
The attack, in which Dome sustained injuries on his hands, came a day after CPM state secretary Surjya Kanta Mishra, who heads the Opposition in the West Bengal Assembly, was heckled by people reportedly linked to the ruling Trinamool Congress.
Blaming the ruling party for the attacks, Mishra said such attacks would only intensify their movement.
"The Trinamool does not have the capability to stop these jathas (protest march). They will be blown away like chaffs in the wind. The more the attacks, the intenser our movement will be," he said.
The "jathas" also came under attack in West Midnapore's Pingla.
Former CPM Lok Sabha member Sujon Chakraborty claimed at least 20 party activists along with Dome were injured in the twin attacks.
"BPMO jathas were attacked at Mayureswar and Pingla and 20 people were injured, including ex-MP Dome," said Chakraborty.