Kolkata,  On a day when the Election Commission announced the bypolls in Bhowanipur from where Chief Minister Mamata Banerjee will seek to get elected to the West Bengal Assembly, the Trinamool Congress received a boost with another BJP MLA joining the ruling party on Saturday, taking the tally of saffron party MLAs joining the Trinamool camp to four.

Kaliaganj MLA Soumen Roy on Saturday joined the Trinamool Congress in Kolkata in the presence of state minister and party leader Partha Chatterjee.

Justifying his return to the party, Roy said, "I had to contest from Kaliaganj on a BJP ticket due to some circumstances. But my soul and heart belong to Trinamool. I joined the party again to support Chief Minister Mamata Banerjee's efforts. I apologise to the party for the time I was not with it."

Two other BJP MLAs joined the Trinamool in the past one week -- Tanmoy Ghosh from Bishnupur in Bankura district and Biswajit Das from Bagda in North 24 Parganas district.

The first BJP MLA to defect to the Trinamool was Mukul Roy, the party's national Vice President who had won the elections from Krishnanagar North.

While Roy had left Trinamool for the saffron camp in 2017, the other three MLAs were in the ruling party before jumping ship to the BJP just before the Assembly elections held in March-April this year.

Ever since the Trinamool swept the polls to retain power in West Bengal, many leaders who had switched to the BJP from the Trinamool camp before the Assembly polls have returned to the party.