The Health, Labor and Welfare Ministry has stepped up its fight against black baito, or exploitative part-time jobs, amid claims more firms are underpaying and overworking university students to cut costs.

In the latest move in its monthslong campaign to crack down on the practice, the ministry last month warned industry and business lobby groups to improve the treatment of students who are often forced to work marathon shifts in difficult conditions.

Fueling concerns is the view that businesses have grown increasingly reliant on part-time workers, instead of full-time staff, in a bid to cut back on personnel costs.