TOKYO — In surprisingly frank public testimony on Wednesday, Japan’s nuclear safety chief said the country’s regulations were fundamentally flawed and laid out a somber picture of a nuclear industry shaped by freewheeling power companies, toothless regulators and a government more interested in promoting nuclear energy than in safeguarding the health of its citizens.

The disaster at the Fukushima Daiichi plant, stricken by an earthquake and a tsunami last March, has led to widespread criticism of nuclear officials for their lax approach to safety, as well as for a bungled response that allowed meltdowns to occur at three of the plant’s six reactors.

The scale of the accident, which forced almost 100,000 people from their homes and contaminated a wide area of northeastern Japan, has put pressure on the government to explain why warnings about the plant’s safety went unheeded and global safety standards were ignored, even as officials promoted nuclear power as the country’s most reliable source of electricity.