Prime Minister Naoto Kan said Wednesday that Japan needs to increase the independence of its nuclear regulators to ensure safety in the wake of the country's nuclear accident.

In Japan a single ministry is responsible for both promoting nuclear energy and overseeing its safety, unlike most other nuclear power-producing nations which separate the two functions.

Critics say that structure has resulted in lax oversight and may have contributed to a lack of precautions at the Fukushima Dai-ichi nuclear plant, which is leaking radiation after being damaged in March's massive quake and tsunami.

"Entities that promote and check nuclear energy belong to the same government institution, which raises a question of independence," Kan told a news conference where he also promised a thorough review of the nuclear power industry and its regulators.

"We don't necessarily have a sturdy structure in this regard," he said.

An Associated Press review of Japan's approach to nuclear plant safety has also revealed that closely intertwined relationships between government regulators and industry have allowed a culture of complacency to prevail.

Too close for comfort

Top government officials nearing the end of their careers often land plum jobs within the industries they regulated, giving Japan's utilities intimate familiarity with their overseers. Top industry officials are also appointed to positions on policy-shaping government advisory panels.

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Canadian singer Justin Bieber meets Wednesday with schoolchildren evacuated from areas devastated by the March 11 earthquake and tsunami during an event held at the U.S. ambassador's residence in Tokyo. Bieber is in Japan as part of his world tour. ((Shizuo Kambayashi/Associated Press))

Kan's comments are some of the strongest on regulatory reforms since the March 11 quake, although various other senior government officials have raised the issue.

Tokyo Electric Power Co., which operates the damaged plant, hopes to bring it to a cold, stable shutdown by early next year.

The Nuclear and Industrial Safety Agency, part of Japan's trade ministry, ordered TEPCO this week to determine what damage at the plant was caused by the magnitude-9.0 earthquake and what resulted from the subsequent tsunami.

Concerns have grown that the earthquake may have dealt greater damage to the reactors than previously thought, raising questions about claims the plant could withstand major quakes.

Until now, TEPCO has maintained that the tsunami caused most of the damage to the plant, including knocking out its cooling systems, which caused fuel rods to overheat and almost completely melt. Melted fuel then fell to the bottom of the core vessel at each of three reactors, some penetrating the bottom and into the outer chamber.

Since then, workers have been able to keep temperatures in the reactor cores well below dangerous levels by injecting water into them, although holes in the pressure vessels are leaking vast amounts of radioactive water into the lower compartments of the reactor buildings and elsewhere in the complex.