Doctors and nurses at a national medical center in Osaka can work up to 300 hours of overtime per month under a union-management agreement, official data obtained by a lawyer showed Thursday.

The overtime cap is three times the 100 hours per month the government deems as risking death from overwork, a phenomenon commonly known in Japan by the term "karoshi."

Employers and labor unions are required to conclude an agreement on overtime hours if employees work more than eight hours a day or 40 hours a week.

Although the Health, Labor and Welfare Ministry recommends employers cap maximum overtime at 45 hours per month, or 360 hours a year, employers and unions can make an agreement exceeding the levels.

The National Cerebral and Cardiovascular Center says the actual working hours would be around 60 to 70 hours per months but suggested that it may review the agreement.

The lawyer Tadashi Matsumaru, who made the freedom-of-information request, said the union-management agreement dated April 2012 covered around 700 personnel including regular and part-time doctors and some nurses. Under special circumstances, they may work up to 300 extra hours per month and 2,070 hours per year.

Matsumaru slammed the deal, saying "It is based on the premise of making employees work without any rest."

If agreed between employers and unions, there is no legal limit on maximum overtime work hours. But to address the issue of long working hours, the government compiled an action plan in March under which maximum overtime hours should not exceed 100 hours per month.

But the plan exempted doctors from the cap for five years, as they have obligations to treat patients unless there are legitimate reasons.

Koji Morioka, a labor expert and honorary professor at Kansai University, said, "Monthly overtime of 300 hours is excessive and unbelievable. Getting a grip on the realities of labor conditions at medical facilities is urgently needed."