The ruling party's presidential nominee is reviewing whether to include a four-day workweek as a major campaign promise, sparking debate as to whether the pledge is realistic for South Korea.

Former Gyeonggi Province Gov. Lee Jae-myung, presidential nominee for the ruling Democratic Party of Korea, said in an interview with JTBC that he is contemplating a promise to bring in a four-day workweek in a step-by-step manner to improve welfare and employment for South Korean workers.

"Introducing a four-day workweek is something that eventually has to be done to promote humanitarian life and shorter work hours," Lee said during the interview Wednesday.

"It would be a long-term project, but we need to make efforts to implement this soon to keep pace with the fourth industrial revolution."

Under Lee's vision, a four-day workweek could create more jobs and cut the number of work hours, which are among the longest in the world among advanced nations. As of 2019, Korea had the second-longest work hours among OECD member nations: 1,967 hours a year.

Lee said he hopes the private sector will be motivated to hire more employees if work hours are limited. His vision also is seen as a way to overcome his weakness in polls among young voters in their 20s and 30s, who are seen as putting more value on work-life balance.

The four-day workweek vision is also in line with his focus on increasing state-run welfare programs. He has vowed to include universal basic income and basic housing programs among his campaign promises.

He started a test run in September by introducing a 35-hour workweek for the Korea Gyeonggi Corporation, a networking firm partly owned by the provincial government. No results from the test run are available yet.

Although he is not the first presidential candidate to speak of a four-day workweek, Lee is one of the front-runners for next year's presidential election.

Rep. Sim Sang-jung of the minor left-wing Justice Party had already announced her support for a four-day workweek last month. It was her first campaign promise as a presidential contender, and she said it was in line with the global trend of cutting work hours.

Lee’s comments Wednesday immediately drew criticism from the opposition bloc, which said the program could lower wages, cost jobs and negatively impact the business environment for local firms.

"If the sweet mask of the four-day workweek is removed, we will see how the program will cut wages and the number of jobs due to its negative impact on the business environment," main opposition People Power Party Chairman Lee Jun-seok said in a party meeting Thursday.

"It seems that Lee is directly succeeding the economic incapability of the Moon Jae-in administration that has pushed for economically nonsensical policies, making up for loopholes in its theories with help of flatterers and arguing for possibility on impossible with rigged statistics."

A four-day workweek has been the subject of discussion for years, but has only gained traction in the past several years. Several companies here have committed to test runs and cut work hours as a way to improve recruitment, retention and efficiency.

SK Group since 2019 has allowed some of its affiliates’ employees to work four days a week every other week, and Woowa Brothers, operator of food delivery app Baemin, effectively offers a 4.5-day workweek by letting employees take Monday mornings off.

It was a hot enough topic to come up in politicians’ debates and campaign promises during the Seoul mayoral by-election in April as well.

Former SMEs Minister Park Young-sun expressed interest in bringing in a 4.5-day workweek for Seoul workers in her unsuccessful run for Seoul mayor, as did Rep. Cho Jung-hoon of the minor anti-establishment political party Transition Korea.

"Almost all corporations, including those from Korea, saw their productivity rates rise 20 percent (after transitioning to a four-day workweek schedule)," Cho said in a radio interview in February, citing a research paper.

“We would be providing a number of tax incentives and consultative work to motivate small and medium-sized companies considering the transition.”

The public is generally in favor of the idea, as seen from recent surveys.

According to a survey of 4,155 job seekers by human resources service firm Saramin, 83.6 percent of respondents said they had a positive view of the idea of a four-day workweek, citing better work-life balance, higher productivity, improved health and economic growth from more holidays.

But the idea has faced criticism for being too unrealistic and abrupt for Korea, which is already struggling to fully institutionalize a 52-hour maximum workweek system introduced by the current government.

Industrial experts have warned that abruptly introducing it could cause unwanted turbulence in the labor market, cutting wages and forcing employees to find additional wage-earning opportunities, which could undermine the productivity rate for employees and firms alike.

They add that shorter workdays could also take away employment opportunities from those in need, as more people would prefer to commit to two jobs simultaneously.

A growing number of people are already inclined to take on two jobs at the same time, partly due to the COVID-19 pandemic reducing their incomes.

According to a survey of 1,460 workers by FindJob in April, 76.8 percent of respondents said they were willing to commit to two jobs for more income, with many of them preferring to take on part-time jobs in addition to their full-time gigs.