Kolkata, Sep 19 (IANS) The Trinamool Congress' Sougata Roy Tuesday emerged victorious in the by-election to the Bongaon assembly seat, salvaging the party' prestige in the West Bengal assembly.

The Trinamool had lost the status of official opposition party due to its numerical minority in the state assembly following the death of a legislator soon after its debacle in this year's April-May assembly elections.

Of the three Lok Sabha seats, for which by-elections were held Saturday, the Congress is leading in Malda. In the Lok Sabha seats of Purulia and Katwa, the Left Front candidates are leading by unassailable margins and are set to make a clean sweep.

Sougato Roy, who had lost the April-May election from Dhakuria in south Kolkata, defeated Pankaj Ghosh of the Communist Party of India-Marxist (CPI-M) by 5,761 votes in Bongaon in North 24 Parganas district.

The by-election was necessitated by the death of Bhupen Seth of the Trinamool Congress, reducing the party to 29 seats in the assembly.

The counting of votes in the by-elections began Tuesday morning.

Roy's win helped salvage the prestige of Mamata Banerjee's party which needed at least 30 seats in the 294-member assembly to be officially recognised as an opposition.

An opposition without recognition is not entitled to table a no-confidence motion against the government.

"There was no anti-Left candidate in Bongaon. The Congress also helped us. Bongaon helped show that if anti-Left votes are not split, then we can win. We also encashed on the sympathy following the death of Bhupen Seth," said Roy. He had initially faced opposition from Seth's son, who opposed his candidature as an outsider.

"We will be more scathing in the assembly now," said Roy, whose oratory was missed in the new assembly.

The by-elections from Malda and Katwa (in Burdwan district) were necessitated by the deaths of veteran Congress leader A.B.A. Ghani Khan Chowdhury and Mehboob Jahedi of the CPI-M respectively.

The by-election from Purulia arose from the conviction of All India Forward Bloc MP Bir Singh Mahato in a rape case.