The BJP Monday took control of the South Dinajpur Zilla Parishad in West Bengal from the TMC, its first in the state, after majority of its members, besides an MLA, switched sides.
In a jolt to the TMC in South Dinajpur district, veteran leader Biplab Mitra also joined the BJP.
Mitra who was considered to be one of the architects of the Trinamool Congress in the district in north Bengal, was shunted out as the party's district president after the Lok Sabha polls.
Besides Mitra and 10 of the 18 members of South Dinajpur Zilla Parishad, TMC MLA Wilson Champramary joined the BJP at its headquarters in Delhi.
Champramary who represents the Kalchini constituency in Alipurduar district joined the BJP in the presence of its senior leaders, including Mukul Roy, West Bengal president Dilip Ghosh and its national general secretary Kailash Vijarvargiya, who is in charge of its state affairs.
Champamary is the fifth TMC MLA to have joined the BJP recently. One legislator each of the CPI(M) and the Congress have also switched over to the BJP.
Roy described the joining as an "earthquake", saying almost all members of the Zilla Parishad, including its chairperson Lipika Roy, are in the BJP now.
A number of TMC leaders have joined the BJP after it emerged as a strong challenger to the state's ruling party by winning 18 Lok Sabha seats of the total 42 there.
Mitra said the TMC was functioning in an "autocratic way" and has lost its contact with the people.
"The TMC has become a party of arrogant autocratic leaders. I had built the party in the district from scratch from 1998 but I was made to feel like an outsider in the party. My hard work of so many years was not respected," he said.
He hinted that several other TMC leaders from north Bengal are also likely to join the BJP soon.
The BJP had won six of the seven Lok Sabha seats in north Bengal this time, including the Balurghat constituency in South Dinajpur district.
Reacting to the development, senior TMC leader Firhad Hakim said those who have joined the BJP are opportunists and they will repent in the days to come.
"If they have guts, they should resign from their post as elected representatives and fight polls," Hakim said.
Buoyed by major gains in Lok Sabha polls in West Bengal, the BJP leadership is aiming for more than two-third majority in the assembly elections due in 2021 and also for early polls in the state.
The party's vote share zoomed to 40.25 per cent in the Lok Sabha polls of 2019 from 17 per cent in 2014.
The BJP's gains were even more impressive in the assembly bypolls, which were held along with the Lok Sabha election, where it won four out the eight seats, while the TMC won three and the Congress one.