Dinesh Trivedi joined BJP at its headquarters in New Delhi in the presence of party chief JP Nadda.
Slamming its former Rajya Sabha MP Dinesh Trivedi for switching over to the BJP, the Trinamool Congress on Saturday said he is "ungrateful" and has backstabbed the ruling party in West Bengal ahead of the assembly polls.
Mr Trivedi quit from the upper House of Parliament last month, saying he was feeling suffocated in the Trinamool Congress and was unable to bear various incidents that are happening in the state.
Earlier in the day, he joined the BJP at its headquarters in New Delhi in the presence of saffron party president JP Nadda.
Reacting to the development, Trinamool Congress spokesperson Kunal Mr Ghosh said, "For the last so many years, he (Mr Trivedi) did not say anything. Now, just before the state assembly polls, he has made complaints about the party. He is ungrateful and has betrayed people of the state."
"He held several posts of the party and was entrusted with many responsibilities. At a time when he should repay the Trinamool Congress, he has backstabbed it," Mr Ghosh said.
Mr Trivedi was once a close confidant of West Bengal Chief Minister and Trinamool Congress supremo Mamata Banerjee and was her choice for holding the important railway ministry portfolio in the Union Cabinet during the UPA government.
Echoing Mr Ghosh, Trinamool Congress Lok Sabha MP Sougata Roy said, "People like Trivedi enjoy power during their tenure and leave a party at the time of elections."
Several TMC leaders have quit the party in recent months to join the BJP as the saffron party mounts an aggressive all-out campaign to end Ms Banerjee's 10-year-old reign in the state.
Apart from Mr Trivedi, two former state ministers - Suvendu Adhikari and Rajib Banerjee - had quit the Trinamool Congress and switched over to the BJP recently.
Since the 2019 Lok Sabha polls, 19 TMC MLAs and a Lok Sabha MP of the party had joined the BJP.
Elections to 294 assembly seats in West Bengal will be held in eight phases, beginning on March 27. Votes will be counted on May 2.