Following declaration of the West Bengal Assembly polls results on May 2, several saffron party MLAs, including then national Vice President Mukul Roy, have switched over to the Trinamool.
A senior party leader said that in the last five months, five BJP MLAs have left the party to join the Trinamool and after Sunday's results - where Banerjee defeated her BJP rival Priyanka Tibrewal by a record margin of 58,832 votes, as against 54,213 victory margin she secured in 2011, they are expecting some more sitting legislators and leaders to join the ruling party.
Last month, former union minister and BJP MP Babul Supriyo had also joined the Trinamool.
"After Mukul Roy leaving us, we have realised that few more will leave us. After Banerjee's victory, we expect more, especially those who joined the BJP before Assembly polls, will join Trinamool in coming days," the party leader said.
There is speculation that many BJP MLAs are in touch with the Trinamool leadership, and another senior party leader said that BJP state leadership is trying their best to stop these leaders from leaving.
"But the way our MLAs joined the Trinamool, it seems the state leadership is not able to change their decision of leaving us. But we are trying to stop as many as possible from joining the Trinamool," the leader said.
In June, Mukul Roy, who won from Krishnanagar North assembly seats, left the BJP to rejoined the Trinamool. In September, three BJP MLAs - Tanmoy Ghosh from Bishnupur, Biswajit Das from Bagda, and Soumen Roy from Kaliaganj followed suit.
BJP MLA from Raiganj Krishna Kalyani had recently announced that he had decided to leave the party.