Both leaders had deserted the party and joined Trinamool Congress chief Mamata Banerjee's camp.

The Congress had appealed to the Speaker that action must be taken against the duo under the Anti-Defection Act.

According to sources in the Opposition camp, the development might have some impact on the ongoing talks on the Congress-Trinamool electoral tie-up for the ensuing Lok Sabha polls.

Mitra, former president of West Bengal Pradesh Congress Committee, had parted ways with the Congress to form his new party — Pragatishil Indira Congress (PIC) — immediately after the May 2008 panchayat polls. He joined Trinamool-led West Bengal Secular Democratic Front last July.

Bandopadhyay, who was earlier a Trinamool parliamentarian, had quit the party just before the 2004 Lok Sabha polls and joined the Congress. He managed a nomination from the Congress in the 2006 Assembly polls and won from Bowbazar constituency. He quit the party to join the TMC in December 2008.

After joining Mamata's camp, the Congress Legislature Party promptly urged the Speaker to expel them from the Assembly. Congress Legislature Party leader Manas Bhuniya told mediapersons that since they won the election on a Congress ticket, it was obvious that they would be expelled from the party.

Sources in the Congress said Bhuniya was instrumental in ensuring that action is taken against the two legislators. "It is a signal for other legislators who have plans to quit the party to get a ticket from Mamata Banerjee," said a Congress leader.

Reacting to the Speaker's decision, Mamata said the Speaker had acted as a CPM leader and not as a guardian of the Legislative Assembly. "This action was undemocratic and vindictive on part of the Speaker," said Mamata.

"Our support is with both leaders who will show their popularity in their constituencies," she said, referring to the upcoming Lok Sabha polls.

Bandopadhyay, however, said the termination of his membership cannot be valid because he had already submitted his resignation earlier in the day.

On the other hand, Halim said the membership of both the members was terminated as they were disqualified under the Anti-Defection law.