More than 20 sitting lawmakers face trials on charges of violating the public election law while campaigning for the previous parliamentary elections in April.

Prosecutors said Thursday they indicted seven lawmakers of the ruling Democratic Party (DP) and 10 of the main opposition People Power Party and several others on charges of breaching the Public Official Election Act during their campaigns for the April 15 parliamentary elections.

The measures were taken en masse before the statute of limitations for election law violations in the April polls expired at midnight.

Among the seven DP lawmakers were Reps. Jin Sung-joon and Lee Kyu-min, who were accused of illegal pre-electioneering and making a false accusation against a rival candidate, respectively.

The 10 PPP lawmakers include Reps. Ku Ja-keun and Kim Byong-wook. Ku allegedly made an illegal deal to give a job as an aide in return for election support during his campaigning while Kim was accused of pre-electioneering.

Several other lawmakers, including at least four independent lawmakers and one from the minor opposition Justice Party, were also charged with breaching the election law during the parliamentary polls, according to prosecutors.

While the ruling party appeared to play down the indictment cases against its members as "not too many" compared with previous elections, the reaction from the main opposition party was apparent frustration.

Commenting on the issue on Thursday, PPP spokesperson Kim Ye-ryeong accused the prosecution of "trying to menace" the main opposition party by charging its members en masse while being benign with the ruling party.

Rep. Kim Byong-wook of PPP also denounced the prosecution charge against him as "politically driven."

At stake for the PPP in the election law violation cases is the party's power to veto a potential attempt to amend the Constitution by the ruling party, which holds an absolute majority of 174 seats in the 300-member parliament.

By law, revising the Constitution requires approval by two-thirds of the incumbent lawmakers before the bill becomes available for a referendum for final decision.

For the PPP, currently holding 103 seats, losing more than two seats means it no longer has the 101 seats needed to safeguard its sure-fire veto power.

Under the current law, lawmakers are deprived of their parliamentary seats if they are sentenced to a fine of 1 million won (US$872.80) or heavier punishments for violating the Public Official Election Act or the Political Funds Act.

The Moon Jae-in government and the ruling party are widely expected to embark on a plan to revise the Constitution during the incumbent National Assembly's four-year term that started in late May to allow presidents to seek a second term.

As part of his campaign pledge aimed at reforming the political system, Moon vowed to amend the Constitution so that the country's future presidents will serve a four-year term, renewable for another four years, unlike the current single five-year term.

To live up to the promise, Moon proposed a constitutional amendment bill carrying such campaign pledges in March 2018, but the bill was dropped in a plenary parliamentary session in May that year amid a boycott by opposition lawmakers who then called for a Constitutional revision that allows a greater role for the prime minister, not the double four-year presidential terms. (Yonhap)