Rival parties on Tuesday shifted the blame to each other for a parliamentary standoff over a set of disputed bills, portending another unproductive legislative session this month.

The monthlong extraordinary sitting got off to a rocky start on Monday, as the main opposition Liberty Korea Party and Bareunmirae Party boycotted a floor session in protest over the ruling Democratic Party's refusal to quickly pass a revision to the Broadcast Act.

The revision calls for electing the chief of a public broadcaster with approval from two thirds of the total 13 board members -- seven recommended by the ruling party and six by the opposition bloc.

The opposition parties argue the revision will help insulate public broadcasters from political influence, while stressing that it was the Democratic Party that first proposed it in 2016. But the ruling party has hinted that it would link its support for the revision to the passage of another contested bill.

The LKP berated the ruling party for refusing to compromise based on its political calculations ahead of the June local elections.

"The Democratic Party, only engrossed in the preparations for the elections, is taking a partisan position," Kim Sung-tae, the LKP floor leader, told Yonhap News Agency. "It does not show any signs of change in its positions on key bills, including the change to the broadcast act."

The Bareunmirae Party vowed to boycott all key legislative affairs this month, including deliberations on the government's proposal for an extra budget, should its push for the revision to the Broadcast Act founder.

"The Democratic Party (when it was an opposition party in 2016) called for an early passage of the revision (to the broadcast act), but it is reversing itself now that it has become the ruling party," Kim Sam-hwa, the party's spokeswoman, said.

The minor party plans to hold a rally at the parliament to call for the early passage of the revision.

The ruling party appears to be trying to use its backing for the revision bill as a bargaining chip to secure the opposition parties' support for a bill aimed at establishing an independent investigation agency in charge of probing corruption involving senior officials and their families.

The agency is one of President Moon Jae-in's key campaign pledges to diffuse investigative power, currently concentrated in the prosecution, and to curb irregularities among high-level officials from the government, parliament and judiciary.

Countering the opposition parties' attacks, the ruling party excoriated the LKP for "habitually" boycotting legislative sessions.

"The LKP repeats the boycotts like a sort of a ritual whenever a new parliamentary session opens," Kim Tae-nyeon, the party's policy chief, said during a party meeting. "It is very regrettable that (the party) staged the habitual boycott." (Yonhap)