Millions of Japanese homes are preparing for a long hot summer after Japan's government warned that a shortage of electricity generation could lead to mandatory power cuts. Critics say the threat is a ploy to force the restart of the nation's idling nuclear power plants.

With all 54 reactors shut down or destroyed, the authorities could be forced to demand a reduction in power usage of 20 per cent in western Japan, said a government draft document this week, an area that includes the huge Osaka region – home to nearly nine million people.

The last of the reactors went offline for routine maintenance on 5 May, triggering the start of a debate over the country's nuclear future. Nuclear power accounted for about a third of Japan's energy generation before last year's triple meltdown at the Fukushima Daiichi plant. Businesses say they face a summer slump unless the country's utilities crank out more electricity. The head of the Japan Business Federation, Hiromasa Yonekura, has repeatedly predicted that the $5tn (£3.1trn) economy could "collapse" without the nuclear plants.

A local government in Fukui Prefecture this week became the first to vote for a plant restart since the Fukushima crisis began. Prime Minister Yoshihiko Noda sparked condemnation last month when he announced the Oi complex, 225 miles west of Tokyo, was safe to operate. Kansai Electric, operator of the complex, pays about $30m in subsidies a year to the local host community, which also depends on the plant for hundreds of jobs.

Opponents insist Japan should stay nuclear free and have accused the government and utilities of hyping the threat of power cuts ahead of the country's sweltering summer. "The 2012 summer peak in electricity demand can be managed with energy efficiency, proper load balancing, and energy conservation," said Hisayo Takada, a Greenpeace Japan climate and energy campaigner.

Experts have long questioned the safety of nuclear power in a country that experiences 20 per cent of the world's magnitude-6 earthquakes, but last year's crisis seriously damaged public faith in Japan's network of coastal reactors. Opinion polls conducted on the first anniversary of the 11 March disaster found about 60 per cent of people opposed to restarting reactors with 80 per cent expressing distrust in the new safety measures.

The post-Fukushima crisis has already damaged Japan's commitment to cut greenhouse gasses and increased its bill for oil and gas imports, leaving the country with its first trade deficit in three decades