Of the six dissident MLAs, Burman, Biswabandhu Sen, Diba Chandra Hrankhawl and Asish Saha were present when the letter signed by the MLAs was handed over to the Speaker.
Two other MLAs -- Dilip Sarkar and Pranajit Sinha Roy -- were physically not present on the ground that they were unwell but spoke to the Speaker over phone, official sources said.
Burman said all the six MLAs would formally join Trinamool Congress and that TMC General Secretary Mukul Roy has arrived in the state today from Kolkata.
Meanwhile, another dissident Congress MLA Jiten Sarkar, who has resigned from the Assembly, has expressed willingness to join ruling CPI(M), according to CPI(M) state secretary Bijan Dhar.
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Dhar said that Sarkar is a former member of CPI(M) who had won Assembly elections five times on CPI(M) ticket and was Speaker of the Assembly for nine years.
He would be taken back in CPI(M), he said.
In the 60-member House, the Left Front has 50 seats and of the 10 MLAs of Congress, six submitted the letter to the Speaker.
Burman had earlier resigned from the post of the Leader of the Opposition in protest against the Congress-Left tie-up before the West Bengal Assembly elections.