"Five of the six Congress MLAs met me on Thursday and submitted some documents of other assemblies in the country and various courts. They said they have joined the TMC and demanded recognition as the main opposition party," Debnath told reporters.
He said he had met all the six MLAs individually and verified their signatures.
"I have also met state Congress President Birajit Sinha and others and they have also submitted various documents. After consulting the rules and experts, I will take a final decision by August 29."
Besides suspended Congress leader Sudip Roy Barman, other former Congress legislators who met the speaker are Ashish Saha, Biswabandhu Sen, Diba Chandra Hrangkhawl and Pranjit Singha Roy.
Congress MLA Dilip Sarkar, who also recently joined TMC, did not meet the speaker on Thursday.
TMC's Tripura unit chairman Ratan Chakraborty, a minister in the Congress-led state government during 1988-1993, had warned that if the Speaker did not recognise his party as the main opposition party in the assembly and the six rebel Congress legislators as TMC legislators, they would seek the Governor's intervention.
A TMC delegation had also earlier met Governor Tathagata Roy and informed him of the political development in the state.
Roy Barman, along with other party legislators and a large number of leaders, resigned from the Congress in June in protest against the party's alliance with the Left parties for the West Bengal assembly elections.
Another Congress legislator, Jitendra Sarkar, resigned from the Tripura assembly and rejoined the ruling Communist Party of India-Marxist (CPI-M).
A former CPI-M legislator, Sarkar served as Speaker of the Tripura assembly twice in the past -- he had joined the Congress in March 2010.
Meanwhile, Congress's sitting legislator and former opposition leader Ratan Lal Nath denied media reports that he was also joining the TMC.
With the resignations, the Congress's strength in the Tripura assembly has gone down from 10 to three -- the lowest ever -- in the 60-member House.
The ruling CPI-M-led Left Front has 50 lawmakers. The CPI-M alone has 49.
