The 21st National Assembly officially kicked off Friday with a plenary session.

The main opposition United Future Party(UFP), however, walked out in protest of the ruling Democratic Party's(DP) unilateral push to proceed with parliamentary business without a partisan deal on Assembly organization.

The rival parties are at odds over the naming of chairpersons for the Assembly's 18 standing committees. Expressing great pity, UFP floor leader Joo Ho-young said holding a plenary session in the absence of a partisan agreement is unlawful.

Joo said should the DP believe it can pursue whatever it wants with 177 seats in the 300-member parliament, the Assembly will start off on the wrong foot against public demand to handle national tasks in cooperation and coexistence.

Without the UFP's participation, the DP and minor opposition parties elected six-term DP Rep. Park Byeong-seug as the speaker for the first half of the 21st Assembly and fourth-term DP Rep. Kim Sang-hee as one of two deputy speakers.