The number of workers working less than 15 hours a week reached an all-time high in May.

According to a report released Tuesday by Rep. Choo Kyung-ho of the main opposition People Power Party(PPP), a total of one-point-56 million people nationwide worked less than 15 hours a week as of last month. 

This is the largest monthly tally since the government began tracking related data in January 2000.

The lawmaker attributed the surge to employers' preference to hire part-time workers amid a steep hike in the minimum wage during the Moon Jae-in government.

Rep. Choo called on the government to redouble efforts to create more quality jobs instead of focusing on increasing the number of the employed.