Three of South Korea's four major parties, except the majority party, agreed on Wednesday to hold a referendum on the potential revision of the Constitution in tandem with the presidential polls in May, a lawmaker said.

The agreement was reached during a meeting of floor leaders of the Liberty Korea Party, People's Party and Bareun Party at the National Assembly, said Rep. Kim Dong-cheol of the People's Party, who leads a parliamentary committee on constitutional reform.

"(Floor leaders) of the three parties have reached a consensus on holding the presidential and constitutional revision polls on the same day," Kim told reporters.

After the Constitutional Court upheld the ouster of Park Geun-hye as president last Friday, the presidential election is slated for early May.

The debate over constitutional revision has erupted, as politicians and critics claim the current single five-year term presidency has failed to embrace social and political changes since the last revision in 1987.

Supporters of the revision say that the revision should be focused on enhancing power sharing among the three branches of government, arguing that the concentration of power in the president may have given birth to the ongoing political scandal that led to Park's impeachment.

The majority Democratic Party, on the other hand, hesitates to join the move, apparently believing that a referendum will divert public attention from the corruption scandal involving Park and her friend.

Since the outbreak of the influence-peddling scandal that battered Park and her conservative supporters, the Democratic Party has emerged as the most favored party in various polls, beating the conservative Liberty Korea Party which lost its status as the ruling party with her ouster.

The outlook for constitutional revision is unclear for now, as the three parties with 165 lawmakers total are required to muster the support of an additional 35 lawmakers to pass a revision motion through the National Assembly.

A constitutional motion can be tabled with the consent of more than 150 lawmakers and passed by the approval of two-thirds, or 200, of the 300-seat parliament.

As only 30 of the Democratic Party's 121 lawmakers are known to support the revision, the three parties will still be short five or more consent votes in the plenary polls. (Yonhap)