The Diet on Saturday passed a controversial bill to overhaul the immigration control law, adopting changes meant to provide the graying nation with a supply of foreign workers in what are often viewed as blue-collar sectors.

The revised law marked a drastic policy shift in immigration-shy Japan, paving the way for an influx of an estimated 340,000 foreign workers in the five years after the new visa system comes into effect in April next year.

But the bill, which dominated discussions in the current extraordinary Diet session, has elicited a fierce backlash from opposition lawmakers, who say it is void of key specifics. In its provisions they see an echo of the state-sponsored foreign trainee program, which is rife with allegations of human rights violations including below-minimum wages, bullying and sexual harassment by employers along with harsh working conditions.