The government wants to extend the maximum working week from 52 hours to up to 69 hours at busy times.
Employers will be allowed to offer flexible working hours not only weekly, but monthly, quarterly and longer so that they can put their staff to work for longer hours at times with a heavy workload and have them take a long rest when the workload is light.
But average weekly working hours are to remain within the 52-hour limit.
The government on Monday proposed its first labor bill, which will be submitted to the National Assembly around June.
But the majority opposition Minjoo Party, which was behind slashing the working week in the first place, is unlikely to consent, and the Federation of Korean Trade Unions and the Korean Confederation of Trade Unions have already protested, calling the idea a license to "work staff to death."
Currently, employees cannot work for more than 52 hours in any given week even if they want to, but the new system would allow them to exceed that limit one week or month and make up for it the next.
In an effort to reduce Korea's 1,928 yearly working hours, which is 38.9 days more than the OECD average, the government also wants to introduce a new sabbatical system so workers can compensate for overtime with paid leave.
"The current working-hour system is incompatible with the digital revolution and changing work and lifestyles," the Ministry of Employment and Labor said. "We need to give employers and workers more autonomous discretion in changing times."
