A day after expelling Lok Sabha Speaker Somnath Chatterjee from the party, Communist Party of India-Marxist (CPI-M) general secretary Prakash Karat on Thursday said his party had "no option" other than to take disciplinary action against the senior leader.

"It is unfortunate that we had to take the decision (to expel Chatterjee). But we had no other option," Karat told the media in Hyderabad.

He said his party "did not want to say anything that will create controversy about the speaker's post".

"I have stated that it is for the speaker to decide whether or not to continue. It is up to him. But whether he will continue as a party member is a decision that we (the CPI-M) will take," said Karat who has been in the eye of a storm following the crisis over the India-US civil nuclear deal and subsequently Chatterjee's expulsion from the party.

Chatterjee had been associated with the CPI-M for 40 years.

For the first time since the row over Chatterjee's continuance as speaker erupted, Karat outlined the proceedings that had taken place within his party leading to his expulsion.

The CPI-M leadership wanted Chatterjee to give up the post of Lok Sabha speaker after the 59-bloc Left Front withdrew support to the UPA government.

"From July 9, 2008, we became part of the opposition. The central committee at its two-day meeting on July 19 and 20 decided that no party member should remain speaker after the Left parties had withdrawn support to the United Progressive Alliance (UPA) government," said Karat.

He reminded that Chatterjee became speaker at the request of the ruling Congress and because the CPI-M was part of the Left Front supporting the government.

"After the central committee meeting we communicated our decision to Chatterjee. But he did not want to step down," said the CPI-M general secretary.

He added: "The central committee had authorised us to take a decision. We did not want to do so during the special session and waited till it was over to take the disciplinary action."