Kolkata, Aug 21 - West Bengal's main opposition party Trinamool Congress bagged both seats in this metropolis with impressive margins over the ruling Left Front in the by-polls to the assembly held Aug 18.

Trinamool nominee Swarnakamal Saha beat Communist Party of India's Prabir Deb by 21,557 votes in Sealdah.

In Bowbazar constituency, Trinamool's Sikha Mitra got 15,000 votes more than the Left Front-supported independent candidate Minati Gomes.

The by-polls became necessary after Congress legislators Sudip Bandyopadhyay and Somen Mitra were disqualified by Speaker H.A. Halim under the anti-defection law for crossing over to the Trinamool Congress.

Both of them are now Trinamool Congress Lok Sabha members. Sikha is Somen Mitra's wife.

The Trinamool Congress victory margin appeared all the more impressive as only 41 percent vote was cast on an average in the polls.

The results indicated a further slip in Left vote, as the Trinamool candidates won by a higher margin than Bandyopadhyay had in these assembly segments when he won from the Kolkata North Lok Sabha constituency in May.