The vehicle in which Punjab BJP chief Ashwani Sharma was travelling was attacked by 30-40 people with bricks and sticks near the toll plaza in Hoshiarpur town on Monday evening, police said.
Sharma, who escaped unhurt, termed the attack as an attempt to defame farmers.
"The attack was made as part of the conspiracy to defame the farmers," he told the media.
He said some vehicles were chasing him from Jalandhar when he was on way back to Dasua town.
Condemning the incident, Chief Minister Amarinder Singh said he asked Director General of Police Dinkar Gupta to identify the accused and arrest them.
"Won't allow anyone to disturb state's peace and take law into hands," he said in a tweet.
BJP leader Tarun Chugh blamed the Youth Congress for the attack as guise as farmers to protest against the contentious farm laws.
However, the Chief Minister said there was no question of involvement of the Youth Congress in the attack, and that the BJP should refrain from "frivolous and politically motivated allegations".
"This is highly irresponsible as the Punjab Police are investigating the case," he added.