The party cracked the whip hours after Roy junior expressed doubts over whether his party had faith in him and praised his father.
"Our party has seen Shubhrangshu Roy, young MLA and Mukul Roy's son, not once or twice but on several occasions praising another party by demeaning his own party. Consequently, the Disciplinary Committee in the party has suspended him for six years," Trinamool Secretary-General Partha Chatterjee told reporters.
Chatterjee said Roy's words were inimical to the party's interest and he had continued making anti-party comments.
"I am not leaving the party but I don't know whether my party has faith in me," Subhrangshu Roy told the media at Kanchrapara in North 24 Parganas district.
He spoke about his failure to provide a lead from his Assembly segment Bijpur to the party's Lok Sabha candidate from Barrackpore Dinesh Trivedi, who lost to his BJP rival Arjun Singh.
He said: "I have been defeated by my father. But I don't blame anyone, nor do I have any grief or anger."
According to him, both he and his father have done the best for their respective parties. But people have chosen his father.
"Many people had said that if one Mukul Roy leaves, they will make hundreds of Mukul Roys. I just want to say, Mukul Roy who was there since the inception of the party has now single-handedly destroyed it," Roy added.
Asked if Subhrangshu Roy would join the BJP, Mukul Roy said: "This is something that has to be decided by him and the BJP leadership."
( With inputs from IANS )