In a break from tradition, West Bengal chief minister Mamata Banerjee was on Thursday administered the oath as a member of the state assembly by Governor Jagdeep Dhankhar.
Banerjee, who won the Bhabanipur by-poll by a margin of 58,835 votes, a record for the seat, took the oath in Bengali.
She needed to win the election to retain the chief minister's chair after her defeat at the hands of protege-turned-rival BJP's Suvendu Adhikari in the March-April assembly elections.
Two other newly elected TMC legislators Jakir Hossain and Amirul Islam also took oath soon afterwards.
Jakir Hossain was declared victorious by a huge margin of 92,480 votes from Jangipur, Amirul Islam won from Samserganj by 26,379 votes.
Dhankhar had on Tuesday said he will administer the oath to Banerjee and others, in a departure from the practice of the governor authorising the speaker of the assembly to conduct the exercise.
No MLA of the main opposition BJP attended the oath-taking ceremony.
Leader of the Opposition Suvendu Adhikari said BJP legislators were absent as they did not attach much importance to the oath-taking ceremony of an MLA who had won in a by-poll.
Reacting to the absence of BJP MLAs, West Bengal parliamentary affairs minister Partha Chatterjee told reporters "the party which was dreaming to get 200 plus seats in the assembly polls, the party which talks about parliamentary democracy, has shown their scant regard for parliamentary norms". The absence of BJP lawmakers also reflect their scant regard for the governor's post, he said.
However, BJP MLA Mukul Roy, who had switched over to the TMC a few months back, was present at the oath-taking ceremony.
Dhankhar was greeted on his arrival by both Mamata Banerjee and Speaker Biman Banerjee, who escorted him inside the house.
After the oath-taking ceremony was over, the governor spent around 20 minutes in the speaker's chamber in the presence of the chief minister and parliamentary affairs minister Partha Chatterjee.
Mamata scores landslide victory, TMC sweeps bypolls
Centre conspired to remove TMC from power: Mamata
Why Mamata left the Congress!
Mamata all set to take the battle to BJP in UP polls
Mamata stuns BJP, leads TMC to landslide victory