Shatrughan Sinha said he was "grateful to Asansol's people and to Mamata Banerjee for this victory".
Trinamool's Shatrughan Sinha and Babul Supriyo registered big and handsome wins in Asansol Lok Sabha and Ballygunge assembly seats, respectively, the most keenly watched among the five by-polls for which votes were counted today.
Shatrughan Sinha won the Asansol seat by a margin of 3 lakh plus votes, registering the party's first-ever electoral victory in the constituency. BJP's Agnimitra Paul was the challenger in Asansol.
Babul Supriyo, who vaulted from the BJP, was a winner in the Ballygunge constituency. The BJP had fielded Keya Ghosh while Saira Shah Halim was the CPI(M) candidate in the bypoll.
The by-polls, which took place on April 12, were necessitated as Mr Supriyo resigned as the MP of Asansol after switching over to the Trinamool from the BJP, while state minister Subrata Mukherjee, who represented Ballygunge, died last year.
"Wish to see the faces of those jealous BJP 'Netas' who never acknowledged my hard work for a place I love-Asansol & mocked me by saying, "Even a Matchstick standing for @BJP4India wud win in Asansol. Love you Asansol for serving them a Slap in a platter," tweeted Babul Supriyo.
In Asansol, "Shotgun" Sinha said he was "grateful to Asansol's people and to Mamata Banerjee for this victory."
Meanwhile, Ms Paul said "accept people's verdict, can't say there was rigging... we have to prepare for the 2024 polls taking into account this election."
West Bengal Chief Minister and Trinamool chief Mamata Banerjee thanked voters for giving a decisive mandate to Trinamool candidates in both the seats. She visited the famous Kalighat Temple later in the evening.
"I sincerely thank the electors of the Asansol Parliamentary Constituency and the Ballygunge Assembly Constituency for giving decisive mandate to AITC party candidates," she tweeted.
"We consider this to be our people's warm Shubho Nababarsho gift to our Ma- Mati- Manush organization. Salute to the voters for reposing faith in us, yet again," she added.
Shatrughan Sinha bagged 6,56,358 votes while his BJP rival Agnimitra Paul managed to get 3,53,149, according to the Election Commission website. CPI(M)'s Partha Mukherjee pocketed 90,412 votes and Congress's Prasenjit Puitandy of the Congress got only 15,035 votes.