TOKYO (REUTERS) - Japanese police arrested a businessman on Wednesday for sending a 15-year-old boy to help clean up radioactive waste outside the wrecked Fukushima nuclear plant.

The Aichi prefectural police said the boy, from Kitanagoya City, western Japan, was sent to Fukushima to cut contaminated leaves and scrape up dirt in the disaster zone last July.

Japan's labour law prohibits people under 18 from working in radioactive areas.

The boy told the Asahi newspaper that he was introduced to his former boss through a government-run employment agency and ordered to lie about his age.

He said his former employer eventually lowered his wages to just US$30 (S$ 37.51) a day and hit him when he did not do well at his job.

Workers cleaning up villages in Fukushima are supposed to receive a special hazard allowance equivalent to about US$90 a day from the government in addition to their wages.

An earthquake and tsunami in March 2011 destroyed the Fukushima Daiichi plant, 220 km northeast of Tokyo, sparking triple nuclear meltdowns, forcing more than 160,000 residents to flee nearby towns and contaminating water, food and air.

Thousands of workers have been clearing waste from towns closest to the plant in the past four years.

A Reuters investigation showed how Japan's traditional subcontracting structure in the construction industry opened up lucrative clean-up contracts in Fukushima to multiple layers of small companies that regularly skim workers' pay.