The 500-page report, released Monday by a government-appointed investigative panel, was the result of interviews with hundreds of utility workers and government officials.
A magnitude-9 earthquake and resulting tsunami on March 11 led to a meltdown at the Fukushima facility, the worst nuclear catastrophe since Chernobyl.
"TEPCO did not take precautionary measures in anticipation that a severe accident could be caused by tsunami such as the one (that hit Fukushima) … Neither did the regulatory authorities," the report states.
Regarding the No. 1 reactor, for example, the report says the task force at the plant and the head office of TEPCO had initially failed to realize that an isolation condenser, intended to cool the reactor during a blackout, wasn't working.
Also, Prime Minister Naoto Kan and his Cabinet ministers weren't informed about the System for Prediction of Environmental Emergency Dose Information, which predicted how the wind would distribute radioactive material that had been ejected from the reactors, the report said.
The report also points to inadequate information gathering and poor communication among the government, regulators and TEPCO as factors that worsened the crisis.
"Authorities failed to think of the disaster response from the perspective of victims," said University of Tokyo Professor Emeritus Yotaro Hatamura, who headed the panel.
In its conclusion, the report said: "The nuclear disaster is far from over."
An editorial Tuesday in Japan's Mainichi Daily News, noting that the interim report fails to depict the entire picture of the accident, called for more specific and detailed information in the final report, due this summer.
In response to the report's finding that the utility should have taken precautionary measures to deal with severe accidents triggered by a tsunami, a TEPCO official was quoted by Kyodo News as saying Tuesday that "it is not exactly right to say that we should have done so before March 11, although in hindsight the steps we had taken were not sufficient."
Also Tuesday TEPCO said it has asked for an additional $8.8 billion in aid from the state-backed Nuclear Damage Liability Facilitation Fund for compensation payments related to the Fukushima disaster.
The fund had earlier agreed to provide $11.5 billion to TEPCO. The company said more funds were needed in part because of government guidelines for compensation to those who had voluntarily evacuated due to the nuclear crisis.