The CPI-M politburo expelled Lok Sabha Speaker Somnath Chatterjee from the party after a meeting on Wednesday. The politburo took the decision following Chatterjee's defiance of not quitting the post of Lok Sabha Speaker after the Left parties withdrew their support to the UPA government. Chatterjee who was a member of the CPM central committee presided over the special session of Parliament in defiance of CPM General Secretary Prakash Karat.