The utility that operates Japan’s crippled atomic plant said Friday that it deserves most of the blame for the country’s nuclear crisis.

In its strongest remarks about its own shortcomings, Tokyo Electric Power Co. (Tepco) acknowledged in a report that it was not adequately prepared to deal with the massive earthquake and tsunami that ravaged northeastern Japan in March 2011. The twin disasters cut power at Tepco’s Fukushima Daiichi nuclear plant, causing meltdowns at three reactors. Massive radiation leaks contaminated air, water and soil around the plant and forced about 160,000 residents to evacuate.

“Our safety culture, skills and ability were all insufficient,” Tepco President Naomi Hirose told a news conference. “We must humbly accept our failure to prevent the accident, which we should have avoided by using our wisdom and human resources to be better prepared.”

The report said Tepco’s equipment and safety provisions were inadequate and that the meltdowns should have been avoided. It also said the company was complacent about safety measures and had delayed upgrading them.

The acknowledgment is a major reversal from the utility’s initial investigation report, in June 2012. In that report, Tepco maintained that the tsunami was mostly to blame for the world’s worst nuclear disaster since Chernobyl, in Ukraine, in 1986. It defended its crisis management and criticized what it characterized as excessive interference from the prime minister’s office.

Following a public outcry, the company launched an internal reform task force, led by Hirose, to reinvestigate the crisis. The task force was overseen by a five-member committee of outside experts, including former U.S. Nuclear Regulatory Commission chief Dale Klein.