Mamata Banerjee has lined up a dharna outside the Naihati Municipality on Thursday to highlight its “capture” by the BJP in the aftermath of the Lok Sabha polls in which the saffron party bagged 18 out of 42 seats in Bengal.

“Didi will be in Naihati tomorrow for protests against the manner in which the BJP is trying to grab democratically elected civic bodies,” said a Trinamul source.

The control of the civic body in North 24-Parganas is set to change as 22 of its 31 councillors belonging to Trinamul joined the BJP on Tuesday. Trinamul-turned-BJP leader Mukul Roy said another seven would follow suit soon, taking the figure to 29.

On Wednesday, alleged BJP activists chanting ‘Jai Shri Ram’ allegedly stormed the office of Ashok Chatterjee, the municipality’s chairman, and locked the door after deactivating CCTV cameras. Chatterjee wasn’t present at the time.

“This is nothing but unethical capture of the civic body. They locked up my office, vandalised the building,” said Chatterjee, who later rushed to Calcutta to meet municipal affairs minister Firhad Hakim.

Chatterjee claimed he had not been able to go back home since the Lok Sabha results on May 23. The municipality falls under the Barrackpore Lok Sabha seat, which the BJP snatched from Trinamul this time. The BJP also won the Bhatpara bypoll in the vicinity.

Ganesh Das, former chairman-in-council and the first to defect to the BJP, denied Trinamul’s allegations. “They (those who stormed the office) are Chatterjee’s men who wanted to delete some documents from a laptop in the chairman’s office but could not succeed. They managed to takeaway the hard disc of the CCTV cameras to destroy proof of his illegal activities.”

A complaint has been lodged against the invasion and an inquiry is on, said an officer of Naihati police station.

Not just in Naihati, the BJP has also managed to swing neighbouring civic bodies in Bhatpara, Halisahar and Kanchrapara. “All these places have been the backyard of former Trinamul Number Two Mukul Roy. He has been active in engineering these defections,” said a Trinamul source.

On Tuesday, three MLAs, 60 councillors and some panchayat functionaries joined the BJP. Roy has promised more defections.

On Wednesday, Bidhannagar mayor and Trinamul MLA Sabyasachi Dutta took a swipe at party colleague and minister Sujit Bose for not being able to ensure a lead from his area, Bidhannagar, in the Lok Sabha polls. “Those who could not ensure leads are getting rewarded,” said Dutta, referring to a ministerial shuffle on Tuesday.

Bose was made minister of state in charge of the forest department in addition to his responsibilities as fire services minister.