Japan's former prime minister has warned against the use of nuclear energy.

"I would like to say to the Japanese and to the world -- the safest nuclear policy is not to have any nuclear plants," former Prime Minister Naoto Kan said Monday before a parliamentary panel.

The committee is investigating the government's handling of the Fukushima nuclear power plant, which was knocked out by last year's March 11 earthquake and tsunami.

The last of Japan's nuclear reactors, the No. 3 Tomari reactor in Hokkaido, was shut down this month for maintenance work, marking the first time Japan was without nuclear power production since 1966, when the country's first reactor began operation.

The rest were taken offline for scheduled checkups but have stayed offline due to safety concerns sparked by Fukushima, the worst nuclear crisis since the 1986 Chernobyl disaster in Ukraine.

Kan resigned last August amid mounting criticism of his handling of the crisis. Kan's successor, Yoshihiko Noda, has pledged to reduce the nation's reliance on nuclear power as much as possible.

While Kan apologized for the disaster in his testimony, he pointed a finger at the government and its pursuit of nuclear energy.

"The nuclear crisis was caused by a nuclear plant which was operated under the national policy," Kan said. "I believe the biggest percentage of blame lies with the country."

Yet Kan said, "As the prime minister at the time of the accident, I apologize for my failure to stop it."

"It is impossible to ensure safety sufficiently to prevent the risk of a national collapse," he said. "Experiencing the accident convinced me that the best way to make nuclear plants safe is not to rely on them, but rather to get rid of them."

Also Monday, Kansai Electric Power Co. President Makoto Yagi urged Prime Minister Noda to make a decision regarding the restart of the utility's Oi nuclear plant in Fukui Prefecture.

Kansai wants to restart the Nos. 3 and 4 reactors of the four-reactor plant.

Without nuclear power, Japan faces electricity shortages of up to 15 percent during the peak months of July and August, the utility has warned.

Prior to the Fukushima crisis, Kansai had relied on nuclear power for almost half its electricity, the largest share in Japan.

"The final decision is up to the government, or the prime minister," Yagi said in a Kyodo news agency report. "I would like to ask the prime minister to make a bold decision quickly."

Typically, three weeks are required for a reactor to become fully operational, Yagi said.