Tens of thousands of people marched in Tokyo on Monday in the biggest show of public opposition to nuclear power since the start of the Fukushima Daiichi crisis in March.

The protesters, who included residents of Fukushima prefecture, called for the immediate closure of all of Japan's nuclear reactors and a new energy policy centred on renewables.

The demonstration was the biggest the country has seen in years. Police said 20,000 people had taken part, while media reports put the number as high as 60,000.

Among the protesters were the Nobel literature laureate Kenzaburo Oe, musician Ryuichi Sakamoto and actor Taro Yamamoto, who was forced to leave his production company earlier this year because of his opposition to nuclear power.

"We already have enough electricity, even without nuclear plants," Yamamoto said. "If we don't act, Japan will become a disposal site for nuclear waste."

Almost three-quarters of Japan's 54 nuclear reactors are inoperative due to emergency safety checks and regular maintenance. Pro-nuclear groups, including Japan's biggest industry lobby, Keidanren, have warned that the country faces power shortages unless idle reactors are brought back online.

Oe told protesters: "We need to let leaders of major parties and the Japan Business Federation know that we intend to resist [nuclear power]."

Before the Fukushima accident, Japan depended on nuclear for just under a third of its power supply. The government has abandoned plans to increase its share to 50%.

The prime minister at the time of the disaster, Naoto Kan, came out in favour of phasing out nuclear power. In recent media interviews he said that at the height of the crisis he had feared Japan would cease to function as a nation and that 30 million people would have to be evacuated from Tokyo.

His successor, Yoshihiko Noda, has hinted that reactors that pass newly introduced stress tests will go back on line, although he accepts that Japan must also look to other sources of energy.

According to a poll by Associated Press and the market research firm GfK, 55% of Japanese want to reduce the number of reactors, while 35% believe the number should be kept the same. Only 4% wanted an increase, while 3% supported abolition.

Six months after three of Fukushima Daiichi's six reactors suffered core meltdowns, the plant continues to release radiation. The leaks have contaminated the water supply and food chain, and forced the evacuation of 100,000 people living in or around a 12-mile radius of the plant.

Residents of towns closest to the facility have been told it could be years, perhaps decades, before radiation levels are low enough for them to return.

Japan's environment minister, Goshi Hosono, said on Monday that the plant's operator, Tokyo Electric Power (Tepco) would stabilise the reactors earlier than planned. Tepco, which has been heavily criticised for its handling of the crisis, had said it would bring the reactors to a safe state known as "cold shutdown" by mid-January.

"We will move up the existing target period and endeavour to achieve cold shutdown by the end of this year," Kyodo quoted Hosono as telling an International Atomic Energy Agency (IAEA) conference in Vienna.

Hosono, who oversees the government's response to the crisis, confirmed Japan would accept a team of IAEA inspectors due to arrive next month to advise on how to clean up the area surrounding the plant.