Kolkata, July 29 - With both Trinamool Congress and Congress putting up candidates in state Assembly by-polls to two seats in West Bengal, fissures have developed in their four-month-long alliance that decimated the ruling Left Front in the Lok Sabha polls.

The Aug 18 by-elections to the Bowbazar and Sealdah constituencies in the metropolis have been necessitated because two legislators have now become Trinamool Congress MPs in the April-May parliamentary elections.

While Bowbazar legislator Sudip Bandopadhyay triumphed from Kolkata North, Sealdah lawmaker Somen Mira went to the Lok Sabha from Diamond Harbour.

The Congress has staked its claim on the ground that both Bandopadhyay and Mitra were elected to the assembly as its party's nominees in the 2006 elections, before they switched allegiance to the Trinamool in the run up to the Lok Sabha polls.

On the other hand, the Trinamool has built its case around the argument that with both the leaders crossing over to its fold, the party has become the major anti-Left Front force in the two adjoining areas. Both leaders have strong base in their respective constituencies.

While Bandopadhyay managed a lead from Bowbazar even when he contested as an independent nominee from erstwhile Kolkata North West parliamentary seat in 2004, former state Congress president Mitra won Sealdah constituency seven times.

The Trinamool camp also cites the massive lead taken by Bandopadhyay in the Kolkata North Lok Sabha seat from both the assembly segments.

While Trinamool wants to fight both the seats, the Congress has asked for any one of the two seats.

'We want to continue the alliance with the Trinamool. We have left the matter to our high command. If they ask us, we will contest both or even one. But we want one seat at least, leaving the other to the Trinamool,' said state Congress working president Subrata Mukherjee.

None of the Trinamool leaders was prepared to say anything on record about the discord, as party chief Mamata Banerjee was away in Delhi.