The Fukushima nuclear disaster was a "man-made" accident caused by a utility and government regulators who put self-interest before the interest of the public, an independent parliamentary commission reported today after a six-month investigation into the crises.

The 641-page report, the first of its kind with wide-ranging subpoena powers in Japan's constitutional history, is the result of more than 900 hours of hearings and 1,100 interviews with officials, including the former president of operator Tokyo Electric Power Co., or TEPCO, Masataka Shimizu, and former Prime Minister Naoto Kan.

The findings by the Fukushima Nuclear Accident Independent Investigation Commission detail a scathing indictment of TEPCO and the nuclear regulatory agencies that coddled the utility, despite knowing the risks of their purported inaction. It also criticizes Japanese leadership, saying Kan's cabinet "lacked the preparation and mindset to efficiently operate an emergency response to an accident of this scope."

The panel writes the direct causes of the Fukushima accident could have been prevented. Nuclear regulators and TEPCO were aware since 2006 that a large scale tsunami would lead to a power outage at the plant. They also knew the risk of reactor-core damage from the loss of seawater pumps. TEPCO "intentionally postponed putting safety measures in place," while the Nuclear and Industrial Safety Agency and Nuclear Safety Commission essentially looked the other way, according to the investigation.

"We found evidence the regulatory agencies would explicitly ask about the operators' intentions whenever a new regulation was to be implemented," the commission writes. "From TEPCO's perspective, new regulations would have interfered with plant operations and weakened their stance in potential lawsuits."

Three of the plant's six nuclear reactors suffered meltdowns, after the catastrophic earthquake and tsunami knocked out power to the cooling systems last year. More than 80,000 people were displaced as a result of the radiation fallout.

Contrary to TEPCO's own investigation, which cites the tsunami as the main cause of the nuclear accident, the parliamentary report says the quake might have significantly damaged equipment necessary to ensuring safety. TEPCO was quick to blame the "unexpected" tsunami for the accident, not the "foreseeable earthquake" in order to avoid responsibility, the panel writes.

"This was a disaster 'Made in Japan," commission chairman Kiyoshi Kurokawa said in the report's introduction. "Its fundamental causes are to be found in the ingrained conventions of Japanese culture: our reflexive obedience; our reluctance to question authority; our devotion to 'sticking with the program,' our groupism, and our insularity."

The report was issued on the same day a nuclear reactor went back on the power grid in western Japan, for the first time since the Fukushima accident in March 2011.

All 50 of Japan's reactors have been offline since May for maintenance and safety checks, but Prime Minister Yoshihiko Noda has aggressively pushed to bring them back online to avoid power outages during the peak summer months, despite widespread opposition to nuclear power.

Noda has insisted sufficient safety measures are in place, and reactors can withstand another earthquake and tsunami similar to the one that hit Fukushima, but the public has remained skeptical.

The parliamentary panel casts doubt on government assurances, writing "safety of nuclear energy in Japan and the public cannot be assured unless the regulators go through an essential transformation process."