IWAKI, Japan (REUTERS) - A group of Fukushima workers on Wednesday sued Tokyo Electric for unpaid wages in a potentially precedent-setting legal challenge to the utility and its reliance on contractors to shut down a nuclear plant destroyed by the industry's worst accident since Chernobyl.

The lawsuit, filed by two current and two former Fukushima workers, claims that Tokyo Electric Power Co Inc (Tepco) and its contractors failed to ensure workers are paid promised hazard allowances, a court filing showed.

The workers say Tepco allowed subcontractors to skim funds allocated for wages to bolster their own profits on the decommissioning project at the expense of workers.

The lawsuit seeks the equivalent of almost US$600,000 (S$752,226) in unpaid wages from Tokyo Electric and related contractors. It marks the first time that the utility has been sued for the labour practices of the construction companies it employs.

The lawsuit also asks that the 6,000 workers at the nuclear clean-up project either be made effectively government employees, be put on the Tepco payroll directly or be fairly paid.

The lawsuit was filed on Wednesday morning by lawyer Tsuguo Hirota, the four plaintiffs and a group of supporters at a branch of Fukushima court in Iwaki, about 60 km south of the wrecked nuclear plant.

Hirota said he expects two additional workers will join the action immediately and that more could follow.

Japanese law allows for additional plaintiffs with related claims to join an existing lawsuit.

"A year ago, Prime Minister (Shinzo) Abe told the world that Fukushima was under control," Hirota said in an interview. "But that's not the case. Workers are not getting promised hazard pay and skilled workers are leaving. It's becoming a place for amateurs only, and that has to worry anyone who lives near the plant."

Tepco had no immediate comment.