"This is something outrageous and totally illegal. If it's proven true (after investigations), legal action must be taken," Yoshino told Xinhua on Wednesday.
A 24-year-old Vietnamese man, who worked under the Technical Intern Training Program in Japan, has alleged that he had been coaxed into doing decontamination work in Fukushima, according to a recent report of Nikkei, a financial newspaper in Japan.
The man, who requested anonymity, came to Japan in September 2015 and signed a contract to work for a construction company based in Iwate prefecture, with the job requirement specified as engineering and construction work.
Between October 2015 and March 2016, the man was sent to Koriyama in Fukushima prefecture for dozens of times to do decontamination work in a residential area, including digging out soil from ditches, according to the report.
Afterwards, he was engaged in dismantling buildings in an exclusion zone in Kawamata, Fukushima, before restrictions in the area due to high levels of radiation were lifted.
"I wouldn't have come to Japan if I knew I would be doing this (decontamination work)," the Vietnamese trainee was quoted by Nikkei as saying.
He said he came to Japan because he could make more money than in Vietnam and he also wanted to learn the Japanese language, but he had no idea what he would do in Fukushima.
As it had cost him some 1.6 million yen (15,120 US dollars) to come to Japan, about 1 million yen of which was loaned from local banks and other facilities, he could not just go back home even after he learned the truth of his job.
The trainee finally ran away from the construction company in November 2017 due to health concerns about possible radiation, according to Nikkei.
Tokyo-based Zentoitsu Workers Union is assisting the Vietnamese man to hold negotiations with the construction firm seeking compensation worth the amount he would have been paid if he had completed the rest of his three-year contract.
The construction company, however, denied that it had violated labor laws, claiming that decontamination is not beyond the scope of construction work and it was not the only company that makes foreign trainees do decontamination work.
The Ministry of Justice said Wednesday that it has started investigations into the case.
The incident again called into question Japan's Technical Intern Trainee Program, originally designed to help foreign nationals acquire technical skills. However, it has been widely criticized as a platform to attract cheap overseas labor to make up Japan's labor shortage caused by an aging workforce and immigration curbs.
With little legal protection, the foreign trainees are often underpaid, and illegally placed as oyster shuckers, construction workers and other unskilled positions. Many of the indentured work force are exposed to substandard, sometimes hazardous working conditions.
According to government data, as of the end of 2016, there were 230,000 foreigners working in firms and farms across Japan as what Tokyo calls trainees, among whom 38.6 percent were from Vietnam and 35.4 percent from China.