"The confrontation in the constituent assembly meeting on Tuesday morning was a mistake," said UCPN-Maoist chief Pushpa Kamal Dahal, better known as Prachanda.
He said his party will investigate the matter to find out the truth.
Twelve security personnel and two prominent leaders of the ruling CPN-UML were injured and some furniture was broken as the Maoist lawmakers stormed the Parliament in a bid to halt the process of drafting the Constitution through voting.
"We had no intention of starting a fight but the situation got out of control," Prachanda said.
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He said the party had asked its lawmakers to disrupt proceedings but matters got out of hand when ruling party politicians attempted to move ahead with a vote on the terms of the Constitution without forging consensus.
The incident occurred when the ruling parties were trying to push their proposal for a new draft Constitution through voting before tomorrow's deadline.
He said that his party was ready to negotiate on other issues including forms of governance and electoral system if the ruling alliance is ready to ensure ethnic and regional identities will be kept in mind while adopting a federal model for the country in the new Constitution.
"We will not compromise for ethnic identity based federal structure to be incorporated in the new Constitution," he said.