11 councillors of Congress-controlled Cooper's Camp Municipality, led by its chairman Shibu Bayen, in Nadia district joined Trinamool Congress at the party headquarters here in the presence of its general secretary Mukul Roy, giving the ruling party control of the 12-member civic body board.
Congress had retained the municipality with a landslide victory last year, winning 11 out of 12 seats.
Congress' setback, the latest in a series of civic body blows, came days after the party lost Sainthia Municipality in Birbhum district and Krishnagar Municipality in Nadia district to Trinamool because of defections.
Not only councillors from Congress, those from Left Front constituents CPI(M) and RSP were also joining the ruling party "attracted by development initiatives and good governance of the government headed by Chief Minister Mamata Banerjee," Roy said.
PCC President Pradip Bhattacherjee said "we have asked our district chiefs to keep a watch on Congress councillors to prevent defections to Trinamool."