South Korea's main opposition Minjoo Party of Korea said Tuesday it will make an effort to root out irregularities in large businesses, adding that there is a need to limit the exercise of excessive power by the heads of family-run conglomerates.

"The role of the National Assembly is not to speak out for big businesses, but to keep watchful eyes on them," Kim Chong-in, the party's interim leader said, adding the parliament should refrain from defending local conglomerates.

On the ongoing debate over a possible revision of the Constitution, Kim said lawmakers should establish a special committee to discuss the issue, adding the revision cannot be avoided.

The debate includes changing the current single-term, five-year presidential system to two four-year terms, which critics say would help ensure a more stable, responsible executive branch that is able to make more farsighted decisions.

"It is now the time for us to question ourselves if a single five-year term is right for us," Kim said. "The powers centering on only the president have brought various side-effects and built a winner-take-all structure."