Trinamool Congress MP Abhishek Banerjee was slapped and punched at the public meeting.
Mamata Banerjee's nephew and Trinamool Congress Member of Parliament Abhishek Banerjee was slapped and punched by a man at a public meeting in West Bengal's East Midnapore district on Sunday afternoon.
The man was later identified as Debashish Acharya, a resident of Tamluk in East Midnapore.
Mr Banerjee was slapped while he was on stage at the meeting that was being held in Chandipur in East Midnapore district.
Mr Acharya was then beaten up by Trinamool workers and has been admitted to a local hospital.
The party has claimed that Mr Acharya was not a member of the Trinamool Congress but an "outsider".
Mr Acharya was apparently allowed to go on stage after he told party workers that he wanted to take a photo of Mr Banerjee on his phone. It is not yet clear why he attacked Mr Banerjee.
In an official statement, party spokesperson Derek O'Brien said, "The unfortunate incident at a public meeting in Chandipur may have been a plan to attack our MP Abhishek Banerjee and threaten his life. Now, it is up to the administration to inquire into the matter and the law to take its course".
There is some speculation that the incident could have been the result of internal party problems. Some have speculated that the attacker may be a supporter of Trinamool leader Suvendu Adhikari, the party MP from Midnapore's Tamluk.
There is resentment reportedly at the grassroots about Mr Adhikari being replaced as head of the Trinamool Youth Congress some months ago by Soumitra Khan, and more recently by Abhishek Banerjee.
Mr Adhikari has denied any involvement in the incident.