A new study finds there was widespread fear and confusion within Japan's ruling circles in the days after a tsunami disabled the Fukushima Daichi nuclear power plant last year.

The study by a high-profile private sector panel reports miscommunication and a breakdown in trust between senior government officials and the plant's owners, the Tokyo Electric Power Company, or TEPCO. Tetsuro Fukuyama, an adviser to then-prime minister Naoto Kan, is quoted as saying the normal lines of authority collapsed during the crisis.

The report says Mr. Kan and his aides thought at one point it might be necessary to evacuate Tokyo. Officials also considered sending a suicide squad of elderly experts into the highly radioactive plant to see in person what was going on.

The private-sector group, led by Yoichi Funabashi, the former editor in chief of the daily newspaper Asahi Shimbun, is expected to release the full details of its report later this week.

Preliminary copies of the 400-page report obtained by some news organizations contain sharp criticism of the government for its failure to plan in advance for a disaster of such magnitude.

But the harshest criticism is directed at TEPCO itself. The report says top executives of the company at one point wanted to completely abandon the Fukushima plant, leaving the possibility of a chain reaction that would spiral out of control.

The report credits Mr. Kan for insisting that TEPCO keep some staff at the plant to try to control the disaster, which was caused when the tsunami knocked out the plant's cooling systems. Three of the six reactors at the plant suffered core meltdowns, causing radiation to leak into the surrounding air, sea and soil.

The report confirms long-held suspicions that the government did not inform the Japanese public about its worst fears during the crisis. Officials say they wanted to avoid mass panic.

The panel says it received full cooperation from the government and was able to interview 300 officials and nuclear experts.